Showing papers in "Journal of Avian Biology in 2004"
TL;DR: It is suggested that after the last Ice Ages, the blue tit subspecies have colonized Europe from two different southern refuges following previously proposed general recolonization routes from the Balkans to northern and Central Europe, and from the Iberian Peninsula north- and eastwards.
Abstract: Mitochondrial control region sequences from European populations of the blue tit Parus caeruleus were used to reveal the Pleistocene history and the post-glacial recolonization of Europe by the species. The southern subspecies, P. c. ogliastrae was found to represent a stable population with isolation-by-distance structure harboring a lot of genetic variation, and the northern subspecies P. c. caeruleus a recently bottlenecked and expanded population. We suggest that after the last Ice Ages, the subspecies have colonized Europe from two different southern refuges following previously proposed general recolonization routes from the Balkans to northern and Central Europe, and from the Iberian Peninsula north- and eastwards. The two subspecies form a wide secondary contact zone extending from southern Spain to southern France.
768 citations
TL;DR: The primary importance of fatty acids for fueling intense exercise in migratory birds is discussed, the likely limiting steps in lipid transport and oxidation for exercising birds and the ecological factors that affect the quality and quantity of fat stored in wild birds are discussed.
Abstract: Unlike exercising mammals, migratory birds fuel very high intensity exercise (e.g., flight) with fatty acids delivered from the adipose tissue to the working muscles by the circulatory system. Given the primary importance of fatty acids for fueling intense exercise, we discuss the likely limiting steps in lipid transport and oxidation for exercising birds and the ecological factors that affect the quality and quantity of fat stored in wild birds. Most stored lipids in migratory birds are comprised of three fatty acids (16:0, 18:1 and 18:2) even though migratory birds have diverse food habits. Diet selection and selective metabolism of lipids play important roles in determining the fatty acid composition of birds which, in turn, affects energetic performance during intense exercise. As such, migratory birds offer an intriguing model for studying the implications of lipid metabolism and obesity on exercise performance. We conclude with a discussion of the energetic costs of migratory flight and stopover in birds, and its implications for bird migration strategies.
412 citations
TL;DR: Ornithologists incorporating snakes into their ecological or conservation research need to be aware of practical considerations, including sampling difficulties and logistical challenges associated with quantifying snake habitat use.
Abstract: Despite the overriding importance of nest predation for most birds, our understanding of the relationship between birds and their nest predators has been developed largely without reliable information on the identity of the predators. Miniature video cameras placed at nests are changing that situation and in six of eight recent studies of New World passerine birds, snakes were the most important nest predators. Several areas of research stand to gain important insights from understanding more about the snakes that prey on birds' nests. Birds nesting in fragmented habitats often experience increased nest predation. Snakes could be attracted to habitat edges because they are thermally superior habitats, coincidentally increasing predation, or snakes could be attracted directly by greater prey abundance in edges. Birds might reduce predation risk from snakes by nesting in locations inaccessible to snakes or in locations that are thermally inhospitable to snakes, although potentially at some cost to themselves or their young. Nesting birds should also modify their behavior to reduce exposure to visually orienting snakes. Ornithologists incorporating snakes into their ecological or conservation research need to be aware of practical considerations, including sampling difficulties and logistical challenges associated with quantifying snake habitat use.
219 citations
TL;DR: The two reasons that appear at present most likely to explain the greater prevalence of female song in the tropics are: the need for mutual stimulation to achieve breeding synchrony in a relatively aseasonal environment and sex role convergence arising from more long-term relationships and greater fidelity than is usual among north temperate species.
Abstract: In the tropics female birds sing much more frequently than in the temperate north, and sometimes even join their mates to form duets. Why might this be? We discuss how this phenomenon may relate to differences in life history that have been proposed between these regions, highlight likely hypotheses and point to areas of ignorance where studies are needed. The two reasons that appear at present most likely to explain the greater prevalence of female song in the tropics are: (1) the need for mutual stimulation to achieve breeding synchrony in a relatively aseasonal environment and, (2) sex role convergence arising from more long-term relationships and greater fidelity than is usual among north temperate species.
153 citations
TL;DR: The timing of arrival of 81 migratory species in response to the North Atlantic Oscillation was studied at two Finnish bird observatories and suggests that most Finnish migratory birds are able to adjust the timing of spring arrival in responded to climatic change without time delay.
Abstract: The timing of arrival of 81 migratory species in response to the North Atlantic Oscillation (NAO) was studied at two Finnish bird observatories (1970/99). Timing was determined for the first migrants and for the peak of migration, as well as for the early, median and late phases of migration, defined as the dates when the seasonal cumulative sum of birds reached 5%, 50% and 95%, respectively. For most species, the timing of arrival correlated negatively with the NAO in all phases of migration: the correlation was significant for 79% of species studied. Thus, most species arrived in Finland early when the NAO was positive and indicative of mild and rainy winters in northern Europe. Although all phases of migration correlated negatively with the NAO, the correlations were more negative for the early than for the late phases of migration. Since the NAO did not show a significant trend during the study period, the correlations indicate that the timing of birds followed stochastic fluctuations in the NAO. This finding suggests that most Finnish migratory birds are able to adjust the timing of spring arrival in response to climatic change without time delay.
142 citations
TL;DR: Differences in chick growth and survival suggest that higher quality adults may be able to compensate for the disadvantages of late hatching dates and achieve similar reproductive success to that of pairs hatching chicks early, as well as supporting the parental quality hypothesis.
Abstract: Reproductive success declines over the course of the breeding season in many bird species. Two categories of hypothesis have been evoked to explain this decline. The “timing” hypothesis suggests that seasonal declines in breeding success are attributable to the date of laying. The “parental quality” hypothesis suggests that seasonal declines result from the fact that young, inexperienced, or low quality birds breed later in the season. To evaluate the relative importance of timing and parental quality, egg exchanges and removals were used to manipulate hatching dates of common terns Sterna hirundo. Indices of quality, attendance, provisioning rates, and reproductive success of birds in three experimental groups (delayed hatch pairs, advanced hatch pairs, and pairs induced to relay) were compared to those of date-matched controls. Pairs that hatched chicks early raised more chicks than pairs hatching chicks late in the season, regardless of initial laying date. This suggests that hatching chicks early is advantageous in itself. Our results, however, also support the parental quality hypothesis. There was a significant negative relationship between natural laying date and fledging success, independent of hatching date. Differences in chick growth and survival suggest that higher quality adults may be able to compensate for the disadvantages of late hatching dates and achieve similar reproductive success to that of pairs hatching chicks early. We found that pairs hatching chicks late in the season were subject to more incidents of kleptoparasitism than those hatching chicks early. This may be a proximate factor contributing to seasonal declines in reproductive success for common terns, although such a mechanism would not be likely in non-colonial species. Failure to control for egg quality may have biased the results of some prior egg exchange experiments. Additionally, altered cost of incubation may be an unavoidable confounding factor in studies designed to manipulate timing of breeding.
132 citations
TL;DR: All molecular clocks have to be calibrated with reference dates derived either from the fossil record or from geological events, but clock calibrations remain few and sparse as fossils are often lacking and few geological events are clear-cut enough to be suited for the task.
Abstract: The idea of being able to estimate dates, even if only roughly, from DNA or aminoacid sequences is a very appealing one. Ever since Zuckerkandl and Pauling (1965) suggested that mutations in proteins and their corresponding genes accumulate in a clock-like fashion, i.e., that they accumulate over time in a regular manner, biologists have been trying to date events using molecular data. There are many insights in modern biology which are based on these molecular-derived time estimates such as reconstruction of the history of epidemics from extant viral samples (Korber et al. 2000), the calculation of the dates of origin of selected groups of organisms (Cooper and Penny 1997, Bromham et al. 1999), the appraisal of rates of diversification within selected clades (Baldwin and Sanderson 1998, Sato et al. 2001), reconstruction of sources of colonisation and changes in population size (Griswold and Baker 1997), the effects of glacial cycles on speciation (Klicka and Zink 1997) and many more. Most biologists accept molecular clocks at least at a local level, i.e., the idea that some genes behave in a clock-like fashion across a narrow spectrum of taxa (Li 1993). All molecular clocks have to be calibrated with reference dates derived either from the fossil record or from geological events, but clock calibrations remain few and sparse as fossils are often lacking and few geological events are clear-cut enough to be suited for the task. Hence many studies still rely heavily on universal clocks. The best example is the ubiquitous assumption that animal mitochondrial DNA (mtDNA) evolves with a rate of approximately 2% sequence divergence per million years (myr) (Brown et al. 1979). In birds, this rate was originally estimated from RFLP data in geese (Shields and Wilson 1987). Some DNA-sequence studies found a similar rate in geese and other birds, although several more recent studies have come up with rather different estimates (Fig. 1). Nowadays the 2% rate is commonly applied to avian studies, but how truly universal is this clock among birds? Only a handful of avian mitochondrial clock calibrations have been attempted (reviewed by Lovette 2004) because the fossil record is relatively poor for most avian lineages. Nevertheless, although most calibrations cluster around the 2% value, there is considerable variance around that value (Fig. 1). It can be seen from Fig. 1 that calibrations based on events that occurred within the last million years (young calibrations) are faster than those based on events or fossils older than one million years (old calibrations; MannWhitney U test P /0.0082). How can these differences be explained, since a correlation between evolutionary rate and calibration date is not expected a priori? With one exception, young calibrations are based on island colonisations by small nectarivorous birds, namely sunbirds (Nectariniidae; Warren et al. 2003), and Hawaiian honeycreepers (Drepaniidae; Tarr and Fleischer 1993, Fleischer et al. 1998). It could be that estimates based on these taxa are biased, since both sunbirds and honeycreepers are small passerine birds with short generation times and high metabolic rates (generation times and metabolic rates have been proposed as a source of heterogeneity in evolutionary rates; see e.g. Kohne 1970, Sibley et al. 1988, Martin and Palumbi, 1993). It could also be that island populations are more divergent from ancestral populations than neighbouring continental populations are because of their unique population histories, undergoing genetic bottlenecks and founder effects (Carson and Templeton 1984, Thorpe et al. 1994), which would result in an overestimation of the clock calibration. Also, as it is difficult to pinpoint the actual island colonisation event, and given the high vagility of birds, it is often assumed that islands are colonised as early as they emerge, resulting in a minimal estimate of JOURNAL OF AVIAN BIOLOGY 35: 1 /4, 2004
126 citations
TL;DR: It is concluded that early nutrition affects growth rates in young song sparrows, with effects on skeletal size that carry over into adulthood, consistent with the nutritional stress hypothesis.
Abstract: We manipulated the quantity of food provided to hand-reared song sparrows Melospiza melodia from 3 to 18 days post-hatching, a period when young birds in the wild are especially likely to experience nutritional stress. A control group was given unlimited food, while an experimental group was limited to 60% of the intake of the controls. Both groups showed excellent survival. The controls had significantly higher growth rates than the experimentals and fledged significantly earlier. At the end of treatment, controls were significantly larger than experimentals in body mass, tarsus length, and length of the third primary. After treatment ended, when all birds were receiving the same diet, both groups showed a recession in body mass, but the amount of mass lost was significantly greater in the controls. Consequently the difference in body mass between the treatment groups was much reduced after the period of weight recession. As adults, the controls were significantly larger than experimentals in a principal component measure of size that combined six post-mortem bone measurements. Controls and experimentals did not differ in the number of fault bars in tail feathers grown in part during the period of nutritional manipulation, nor did they differ in the degree of asymmetry in bone measurements. We conclude that early nutrition affects growth rates in young song sparrows, with effects on skeletal size that carry over into adulthood. These results are consistent with the nutritional stress hypothesis, which posits that early nutrition affects adult phenotypic quality as well as display attributes.
119 citations
TL;DR: It is proposed that a phylogenetic analysis of morphology and ecological preferences would show that the current taxonomy of grass and bush warblers reflects species’ habitat preferences and morphology related to locomotion and foraging in their habitats, rather than their shared ancestry.
Abstract: We used maximum likelihood analysis of complete mitochondrial ND2 sequences (1041 bp) to clarify the taxonomy and relationships of various species and genera of grass and bush warblers. The tree revealed two clades of grass and bush warblers. One clade was comprised of all four western Palearctic Locustella and two species of Asian Bradypterus. The other clade included five eastern Palearctic Locustella (including the distinctive Sakhalin warbler Locustella amnicola ) and the marsh grassbird Megalurus pryeri . African Bradypterus and Australian little grassbird Megalurus gramineus were distantly related to their Asian congeners. Therefore, current taxonomy of these genera does not reflect their evolutionary history and needs revision. It is proposed that a phylogenetic analysis of morphology and ecological preferences would show that the current taxonomy of grass and bush warblers reflects species’ habitat preferences and morphology related to locomotion and foraging in their habitats, rather than their shared ancestry. Distinct clades were found in grasshopper warbler Locustella naevia and Pallas’s grasshopper warbler L. certhiola . Detailed phylogeographic studies are needed to elucidate the species status of the clades within these two species.
91 citations
TL;DR: It is shown that female European robins Erithacus rubecula greatly outnumber males in southern Iberia, which confirms that this species is a differential migrant with a strong latitudinal segregation of the sexes and is consistent with the hypothesis that social dominance, mediated by differences in size and experience, is important in determining the habitat segregation of sex and age classes.
Abstract: Birds often show some form of social segregation during winter, both at large geographical scales (a consequence of differential migration) and at the regional or local level, when comparing different habitats or micro-habitats. However, our understanding of the mechanisms underlying such patterns is still poor. These issues have been rarely investigated in migratory Old-World passerines, particularly with respect to differences between the sexes. In this study, we show that female European robins Erithacus rubecula (sexed by molecular techniques) greatly outnumber males in southern Iberia, which confirms that this species is a differential migrant with a strong latitudinal segregation of the sexes. Furthermore, sex, age and body size influence the habitat distribution of robins in winter. Subordinate birds (females, juveniles and small individuals) were generally more common in habitats with a greater shrub development, and comparatively scarce in woodlands with relatively little undergrowth. Birds wintering in woodlands were in better condition (assessed by breast-muscle scoring) than birds wintering in shrubland. These results are consistent with the hypothesis that proposes that social dominance, mediated by differences in size and experience, is important in determining the habitat segregation of sex and age classes. The alternative hypothesis (habitat specialization), although not specifically supported by our findings, cannot be ruled out on the basis of the available evidence.
90 citations
TL;DR: This evidence is only tentative until experimental confirmation, but suggests that males are affected by the colour of their mates’ eggs, a possibility not considered hitherto in the study of sexual selection.
Abstract: A recent hypothesis posits that the bright colours of many avian eggs may act like signals of female genetic quality or condition to males in species with biparental care, inducing them to work harder for their offspring. We measured the colour of blue eggs of pied flycatchers Ficedula hypoleuca in Central Spain with a spectrophotometer on the day of laying, and also quantified the provisioning effort by males and females during the last days of the nestling period. Both chromaticity coordinates in the CIELAB colour space (blue to yellow, green to red) showed significant associations with male provisioning rates, explaining more than 20% of variation in male parental effort. Male provisioning rates were positively correlated with nestling condition, thereby potentially contributing to female fitness. This evidence is only tentative until experimental confirmation, but suggests that males are affected by the colour of their mates’ eggs, a possibility not considered hitherto in the study of sexual selection.
TL;DR: None of the genetic hypotheses can explain fully the high level of extra-pair paternity, at least in populations of Mediterranean blue tits, and it is suggested that direct ecological benefits of EPP for females should be tested more often in correlative as well as experimental approaches.
Abstract: A large body of theories on extra-pair paternity (EPP) in birds has proposed four main ‘‘genetic’’ hypotheses to explain this behaviour: the ‘‘good genes’’ hypothesis, the genetic diversity hypothesis, the genetic compatibility hypothesis and the fertility insurance hypothesis. Empirical tests have been scarce, mainly because high sample sizes are difficult to collect. We have tested these hypotheses in three Mediterranean populations of blue tits Parus caeruleus in which 50 � /68% of the broods contained extra-pair young. Results showed that the distribution of extra-pair young among broods was not random, and that survival to fledging of extra-pair young was higher than that of their within-pair sibs. These results support the idea of genetic effects benefiting extra-pair young. However, comparison of cuckolded and cuckolding males showed no significant difference in their body size, age, survival or relatedness with their paired females, and offspring morphometrics did not differ between extra-pair and within-pair young. We conclude that none of the genetic hypotheses can explain fully the high level of extra-pair paternity, at least in our populations of Mediterranean blue tits. We suggest that direct ecological benefits of EPP for females should be tested more often in correlative as well as experimental approaches.
TL;DR: Most of the hour-to-hour and night- to-night patterns of density and vocalization counts are significantly related and the null hypothesis that the patterns of reflectivity measurements and number of vocalizations during nocturnal migration are not related is rejected.
Abstract: Several studies have found that the peak in bird density in the atmosphere during nocturnal migration occurs before midnight, while the peak in vocalizations from migrating birds occurs after midnight, in the hours just before dawn. In a recent study, the patterns of calling from a single species of migrating birds correlated well with the patterns of density estimates of migrating birds. We test the null hypothesis that the patterns of reflectivity measurements and number of vocalizations during nocturnal migration are not related. We sampled radar data and nocturnal flight calls during spring and fall 2000 in northwestern South Carolina and southeastern New York. We analyzed changes in the hour-to-hour patterns of bird density and vocalizations for 556 hours on 58 nights. We also analyzed the night-to-night changes in the patterns of peak hour bird density and peak hour of vocalizations on 32 nights. We found that most of the hour-to-hour and night-to-night patterns of density and vocalization counts are significantly related and reject the null hypothesis. However, despite significant relationships between reflectivity measurements and vocalization counts, a great deal of variation in vocalization counts remains unexplained. These results suggest that factors other than bird density are responsible for the variation in vocalizing by migrating birds.
TL;DR: It is predicted that passerines should have lower stopover site fidelity than geese and waders, and that site faithfulness should decrease with increasing distance from either end of the migratory journey, and results from a long-term study on the stopover ecology of migrant passerines in southern Portugal are presented.
Abstract: Long-distance migrant passerines are well known to often display high levels of philopatry to breeding and wintering grounds. One could expect that similar selective pressures and similar navigation skills would result in their being faithful to stopover sites, a pattern that has been described for several populations of migratory waders and waterfowl. In this paper, we develop the argument that passerines should suffer from higher costs and receive lower benefits from stopover site faithfulness than waterfowl and waders. Based on Alerstam's (1979) "optimal drift strategy" theory and other considerations, we predict that passerines should have lower stopover site fidelity than geese and waders, and that site faithfulness should decrease with increasing distance from either end of the migratory journey. We present results from a long-term study on the stopover ecology of migrant passerines in southern Portugal that support these predictions and show that, for species and populations that neither nest nor winter in this country, few individuals are faithful to the stopover site. On the other hand, populations that included individuals at (or near to) the start or the end of the migratory journey, had much higher return rates. We could not find any evidence that species linked to scarce habitats, such as wetlands, were more site faithful. Our results are in agreement with several other reports, but in apparent contrast to previous conclusions resulting from some studies involving Old World warblers. These differences are discussed and it is argued that there is no solid evidence to suggest that site fidelity should be important for passerines at stopovers far away from breeding or wintering grounds, meaning that there is a large within-individual variability in the precise migratory routes and stopover sequence used each year.
TL;DR: An unbiased assessment of plumage dichromatism in the yellow-breasted chat Icteria virens is presented, which indicated that the plumage pigmentation consisted solely of the carotenoid all-trans lutein and it was found that males have higher concentrations of plumagesCarotenoids than females.
Abstract: Sexual dimorphism or dichromatism has long been considered the result of sexual selection. However, for many organisms the degree to which sexual dichromatism occurs has been determined within the confines of human perception. For birds, objective measures of plumage color have revealed previously unappreciated sexual dichromatism for several species. Here we present an unbiased assessment of plumage dichromatism in the yellow-breasted chat Icteria virens. Chats exhibit yellow to orange throat and breast plumage that to the unaided human observer differs only subtly in color. Spectrophotometric analyses revealed that chat throat and breast feathers exhibited reflective curves with two peaks, one in the ultraviolet and one in the yellow end of the spectrum. We found differences in both the shape and magnitude of reflectance curves between males and females. Moreover, for feathers collected from the lower edge and middle of the breast patch, male plumage reflected more light in the ultraviolet and yellow wavelengths compared to females, whereas male throat feathers appeared brighter than those of females only in the ultraviolet. Biochemical analyses indicated that the plumage pigmentation consisted solely of the carotenoid all-trans lutein and we found that males have higher concentrations of plumage carotenoids than females. Feathers that were naturally unpigmented reflected more UV light than yellow feathers, suggesting a potential role of feather microstructure in UV reflectance.
TL;DR: It is demonstrated that failing to account for the contribution of food availability, renesting, and multiple brooding in studies of avian demography can result in serious underestimates of mean annual fecundity, potentially biasing calculations of population growth rate, source-sink dynamics, habitat quality, or population viability.
Abstract: Nest predation often is reported to be the major cause of nest failure in birds and by extension the predominant influence on annual fecundity. However, other factors such as the ability of some individuals to renest after a failed nest or to lay additional clutches after successful ones, both of which may in turn be influenced by food availability, can also contribute to individual fecundity. We evaluated the relative importance of nest predation, multiple brooding, renesting, and food availability on mean annual fecundity of a migratory songbird population, using AICc from multiple regression models. In a 16-yr study of black-throated blue warblers Dendroica caerulescens, these four variables combined explained 87% of the annual variance in fecundity. Individually, however, food abundance explained more of the variability (35%) than did predation (29%), double-brooding (19%), or renesting (15%). These results suggest that measuring food availability may be essential to understanding annual differences in reproductive output. They also demonstrate that failing to account for the contribution of food availability, renesting, and multiple brooding in studies of avian demography can result in serious underestimates of mean annual fecundity, potentially biasing calculations of population growth rate, source-sink dynamics, habitat quality, or population viability.
TL;DR: A well-supported molecular phylogeny is presented for the swiftlets and their relatives based on DNA sequence data from two mitochondrial genes, which are used to reconstruct the evolution of echolocation and provide strong evidence that the swiftlet group are amonophyletic group.
Abstract: 143.The abilities of some cave-nesting swiftlets to echolocate has traditionally been used toseparate the genus Aerodramus, which includes echolocating species, from the genusCollocalia, thought to lack echolocation. Here we report the discovery of echolocationin a member of the latter genus, the pygmy swiftlet Collocalia troglodytes. We alsopresent a well-supported molecular phylogeny for the swiftlets and their relatives basedon DNA sequence data from two mitochondrial genes, which we use to reconstruct theevolution of echolocation. Our data provide strong evidence that the swiftlets are amonophyletic group. This monophyly plus the presence of echolocation in C.troglodytes indicate that either (1) echolocation evolved much earlier in the swiftletsthan previously thought and has since been lost in most Collocalia taxa, or (2) thisability evolved independently in Aerodramus and Collocalia. Based on our results,echolocation can no longer be considered a useful character for distinguishing thesetwo genera.J. J. Price (correspondence), Department of Biology, St. Mary’s College of Maryland,St. Mary’s City, MD 20686 USA. E-mail: jjprice@smcm.edu. K. P. Johnson, IllinoisNatural History Survey, Champaign, IL 61820 USA. D. H. Clayton, Department ofBiology, University of Utah, Salt Lake City, UT 84112 USA.
TL;DR: The results give support to the ‘forage maturation hypothesis’ and underline the role of body size as an important cause of variations in patch selection in herbivorous Anatidae.
Abstract: Recent findings suggest that herbivores select feeding sites of intermediate biomass in order to maximise their digestible nutrient intake as the result of the trade-off between forage quality and quantity (‘forage maturation hypothesis'). We propose a reformulation of this hypothesis which recognises this trade-off, but also underlines that constraints due to body mass (i.e. metabolism and digestive constraints, size of the feeding apparatus) can lead to variations in grazing patterns. We tested this latter hypothesis experimentally in three species of herbivorous Anatidae of different body mass: the wigeon Anas penelope (in our study c. 620 g), the barnacle goose Branta leucopsis (c. 2000 g), and the greylag goose Anser anser (c. 3500 g). Each species was tested separately from 0600 to 0930 hours, in an enclosure with a mosaic of patches of grass of three different heights: short, medium and tall. The behaviour, and the location (i.e. patch) of each individual were recorded every 5 minutes. Our results show important interspecific differences in intake rates resulting in different feeding site selection: wigeon and barnacle goose fed fastest on the shortest swards, and selected short grass which was also of higher quality. Tall grass provided the highest dry matter intake rate and digestible protein intake for greylag geese, and they preferred these swards. These choices allowed the birds to maximise their digestible nitrogen intake rate rather than dry matter intake rate and our results thus underline the importance of nitrogen as a major currency for foraging decisions in herbivorous Anatidae. Since the birds selected the two extreme sward heights (instead of the medium one), the results give support to our hypothesis and underline the role of body size as an important cause of variations in patch selection in herbivorous Anatidae.
TL;DR: It is suggested that ice sheets linked to major glacial events not only impact genetic structuring in temperate seabirds, but that sea level changes in the tropics associated with these same events have also significantly impacted contemporary geneticStructuring in tropical seabird species.
Abstract: To test the influence of past vicariant events on population genetic structure of the sooty tern Sterna fuscata, we examined sequence variation in the mitochondrial control region of individuals from the Indo-Pacific and Atlantic Oceans. Our analyses indicate a rapid population expansion at a global scale during the last 100 000 years, consistent with global recolonisation during the interstade following the Pleistocene glacial maxima (125 000–175 000 years bp). We estimate islands of the Great Barrier Reef and Coral Sea were colonised no more than 16 000 years ago, most likely in association with the appearance of new breeding habitat following the final Pleistocene glacial retreat (19 000–22 000 years bp). Our results suggest that ice sheets linked to major glacial events not only impact genetic structuring in temperate seabirds, but that sea level changes in the tropics associated with these same events have also significantly impacted contemporary genetic structuring in tropical seabird species.
TL;DR: Masello et al. as mentioned in this paper found that plasma triglyceride levels strongly relate to changes in individual condition and that plasma levels of triglycerides were strongly related to mass change, hatching order and brood size innestlings.
Abstract: 454.Haematology and plasma biochemistry values are useful tools for ecological research.They have been used to investigate the physiological state and the adaptation ofindividuals to their habitat, changes in nutritional state of birds, body condition, thelevel of parasite infestation, male quality, the physical condition of nestlings, etc. In thepresent study we tested the role of haematological and plasma biochemistry values inburrowing parrots Cyanoliseus patagonus (Aves, Psittaciformes) for determiningindividual quality and condition. We measured triglyceride levels, plasma proteinlevels, plasma hue and erythrocyte sedimentation rate of nestlings and breeding adultsin a colony in the north of Patagonia, Argentina. We found that plasma triglyceridelevels strongly relate to changes in individual condition. Plasma levels of triglycerideswere found to be strongly related to mass change, hatching order and brood size innestlings. Levels of triglycerides were found to reflect reproductive effort in adults:males fledging larger broods had decreased levels of triglycerides. Adults with lowerbody condition had increased erythrocyte sedimentation rates. Plasma hue showed astrong relationship with an ornamental trait, the red abdominal patch of male adults,and with parameters of structural body size. Thus, we have shown that haematologicaland plasma biochemistry values, especially plasma levels of triglycerides, are goodindicators of individual quality and condition in nestlings and breeding birds.J. F. Masello (correspondence) and P. Quillfeldt, Institut fu¨rO¨kologie, Friedrich-Schiller-Universita¨t Jena, Germany. Present address of J. F. Masello: Ecology of Vision Group,School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG,UK. E-mail: juan.masello@bristol.ac.uk
TL;DR: Evidence is presented that increased egg production can have long-term effects on female body condition and aspects of reproduction in great skuas, however, although present, the costs of extra eggs appear to have been relatively small in the great skua in comparison to the two other bird species for which inter-annual effects have been reported.
Abstract: We investigated the effects of increased egg production on body condition as well as on measures of reproductive performance in great skuas, Stercorarius skua, over two subsequent years. We experimentally increased egg production from the normal two to six eggs. Six eggs might also be produced under natural circumstances after repeated clutch loss. After the production of the last egg we measured: (i) body mass, (ii) pectoral muscle, and (iii) haematocrit, total red blood cell count and mean corpuscular volume, as indicators of body condition. We took the same measurements of control females who had produced the normal clutch of two eggs. The measurements were repeated one year after the manipulation, and survival, laying dates, clutch sizes and hatching success were recorded for up to three consecutive years. After producing six eggs, females were lighter, had smaller pectoral muscles and lower haematological values than control females. Hatching success of eggs was significantly reduced. Even one year after the experiment there were still differences in body condition. Annual survival was not affected by the manipulations, although there was an indication that survival costs depended on whether chicks were raised after the increased egg production. While pair bonds and egg sizes were not affected in the post-experimental year.. females started breeding significantly later than in the previous year. Two years after the experiment laying dates had advanced again and were not different from those of control females. This pattern of maintaining survival and egg sizes, but delaying breeding in the post-experimental year was found for two independent groups of females which had both been subjected to increased egg production. These results present evidence that increased egg production can have long-term effects on female body condition and aspects of reproduction. However, although present, the costs of extra eggs appear to have been relatively small in the great skua in comparison to the two other bird species for which inter-annual effects have been reported.
TL;DR: A fresh perspective on carotenoid metabolism in animals should aid the efforts to characterize the responsible enzymes and to better understand the localized biological functions of these pigments.
Abstract: For decades, carotenoids have attracted attention for their roles as vitamin-A precursors, antioxidants, and immunostimulants, but we still understand very little about the metabolic processes that accompany these compounds. Animals like birds use carotenoids to color their feathers and bare parts to become sexually attractive. They commonly metabolically derive their body colorants from dietary sources of carotenoids, but the sites of pigment metabolism remain unidentified. Here I test the hypothesis that songbirds manufacture their colorful feather and beak carotenoids directly at these tissues. I offer two lines of evidence to support this idea: (1) in a study of 11 colorful species from three passerine families, metabolically derived feather and beak carotenoids were found neither in the liver (a purported site of carotenoid metabolism), nor in the bloodstream (the means by which metabolites would be transported to colorful tissues from anywhere else in the body) at the time when pigments were being deposited into keratinized tissue, and (2) in a more detailed study of pigmentation in the American goldfinch Carduelis tristis, carotenoids sampled from the lipid fractions of maturing feather follicles yielded a mix of dietary and synthetic carotenoids, suggesting that this is the metabolically active site for feather-pigment production. This fresh perspective on carotenoid metabolism in animals should aid our efforts to characterize the responsible enzymes and to better understand the localized biological functions of these pigments.
TL;DR: Recaptures and dead recoveries of ringed birds showed long distance non-breeding movements to the Central American coast and elsewhere in the eastern Pacific, contrasting with the very limited dispersal to breeding sites.
Abstract: We documented natal and breeding dispersal at several spatial scales by Galapagos Nazca boobies Sula granti, a wide-ranging pelagic seabird. We found exceptionally low degrees of both types of dispersal despite these birds’ vagility. Median natal dispersal distances were 26 m and 105 m for males and females, respectively. Median breeding dispersal distances for both sexes were 0 m. No natal or breeding dispersals occurred from our study site at Punta Cevallos, Isla Espanola to six other colonies in the Galapagos, but we did document four long-distance natal dispersals from Punta Cevallos to islands near the South American coast. Recaptures and dead recoveries of ringed birds showed long distance non-breeding movements to the Central American coast and elsewhere in the eastern Pacific, contrasting with the very limited dispersal to breeding sites.
TL;DR: Cuckoos parasitising four sympatric species of Acrocephalus warblers in southern Moravia, Czech Republic showed a high level of parasitism, egg mimicry and breeding success, but the cuckoo chicks survived better in great reed warbler nests, resulting in a breeding success of 30.4%, as compared to 16.4% in nests of the reing warbler.
Abstract: We investigated the level of parasitism, egg mimicry and breeding success of cuckoos parasitising four sympatric species of Acrocephalus warblers in southern Moravia, Czech Republic. The parasitism rate was highest in the marsh warbler Acrocephalus palustris (44.8%) followed by great reed warbler A. arundinaceus (33.8%), sedge warbler A. schoenobaenus (26.5%) and reed warbler A. scirpaceus (11.6%). Although the cuckoo eggs showed a high level of mimicry the eggs of the marsh warbler this host species rejected 72% of the cuckoo eggs, resulting in a cuckoo breeding success of only 4.3%. Cuckoo eggs laid in great reed warbler and reed warbler nests showed a similar hatching success, but the cuckoo chicks survived better in great reed warbler nests, resulting in a breeding success of 30.4%, as compared to 16.4% in nests of the reed warbler. The relationship between the level of parasitism, host rejection of cuckoo eggs, cuckoo chick survival and breeding success is discussed for the four host species.
TL;DR: Investigation of plasma concentrations of carotenoid-based plumage coloration, sex, habitat, leukocyte hemoconcentrations and infection status with Haemoproteus blood parasites in brood-rearing great tits found results consistent with the idea that maintenance of high blood antioxidant levels might conflict with individual needs to rely on oxidative stress for fighting infections.
Abstract: The concept of parasite-mediated sexual selection assumes that females may improve offspring fitness by selecting mates on the basis of sexual ornaments that honestly reveal the health state of a partner. Expression of such signals may be particularly sensitive to oxidative damage caused by excess production of oxidative metabolites and free radicals. To control and neutralise free radicals, animals rely heavily on dietary fat-soluble antioxidants such as vitamin E and A, and carotenoids. However, the organism's need for free radical scavenging may interfere with the opposite need to generate oxidative stress for fighting parasitic infections. We investigated plasma concentrations of carotenoids and vitamin A and E in brood-rearing great tits Parus major in relation to carotenoid-based plumage coloration, sex, habitat, leukocyte hemoconcentrations and infection status with Haemoproteus blood parasites. Rural great tits differed from urban ones and males from females with respect to the hue of the yellow ventral feathers. However, plasma antioxidant concentrations were not related to sex, habitat or plumage coloration. Plasma carotenoid concentration correlated positively with indices of immune system activation as measured by blood counts of lymphocytes and eosinophils. Birds with gametocytes of Haemoproteus in their blood had higher plasma concentrations of carotenoids and vitamin E than unparasitized individuals. These results are consistent with the idea that maintenance of high blood antioxidant levels might conflict with individual needs to rely on oxidative stress for fighting infections.
TL;DR: These preliminary findings warrant further studies in barn owls and other predators, in both field and laboratory settings, to uncover fine predator head movements during hunting, the corresponding defensive behavior of the prey, and the adaptive significance of thesebehaviors.
Abstract: 116.The present study was aimed at testing a novel idea, that rather than maximizing theirdistance from a predator during close-distance encounters, prey species are better offmoving directly or diagonally toward the predator in order to increase the relative speedand confine the attack to a single available clashing point. We used two tamed barnowls Tyto alba to measure the rate of attack success in relation to the direction of preymovement. A dead mouse or chick was used to simulate the prey, pulled to variousdirections by means of a transparent string during the owl’s attack. Both owls showed ahigh success rate in catching stationary compared with moving food items (90% and21%, respectively). Success was higher when the prey moved directly away, rather thantowards the owls (50% and 18%, respectively). Strikingly, these owls had 0% success incatching food items that were pulled sideways. This failure to catch prey that movesideways may reflect constraints in postural head movements in aerial raptors thatcannot move the eyes but rather move the entire head in tracking prey. So far there isno evidence that defensive behavior in terrestrial prey species takes advantage of theabove escape directions to lower rates of predator success. However, birds seem toadjust their defensive tactics in the vertical domain by taking-off at a steep angle, thusmoving diagonally toward the direction of an approaching aerial predator. Thesepreliminary findings warrant further studies in barn owls and other predators, in bothfield and laboratory settings, to uncover fine predator head movements during hunting,the corresponding defensive behavior of the prey, and the adaptive significance of thesebehaviors.D. Eilam (correspondence) and E. Shifferman, Department of Zoology, Tel-AvivUniversity, Ramat-Aviv 69 978, Israel. E-mail: eilam@post.tau.ac.il
TL;DR: The findings suggest that comb size relates to immune function rather than T. tenuis parasite infection intensity, and males with bigger combs are likely to be of higher phenotypic quality because they are more immunocompetent and might be better able to cope with the detrimental effects of parasites.
Abstract: Sexual ornaments may enable females to discriminate amongst potential mates and choose those having either fewer parasites, or those which are more immunocompetent, or better able to cope with parasites. Tetraonid birds exhibit supra-orbital combs that function in both intra-sexual competition and mate choice. Through a correlative and experimental approach we investigated whether comb size of male red grouse Lagopus lagopus scoticus was related to infection intensity by their main parasite, the gastro intestinal nematode Trichostrongylus tenuis, and to immune function. We first looked at the relationships between immune function, parasite infection and condition. We found that spleen mass, an indirect measure of immune response, correlated positively with T. tenuis load, and negatively with condition. Cell-mediated immunity, a measure of immune defence, correlated positively with condition, and although not significantly related to T. tenuis load, increased when nematode parasites were experimentally reduced. Secondly, we investigated whether comb size was related to condition, T. tenuis load or immune function. Comb size was not significantly related to T. tenuis infection and did not change significantly after nematode parasite removal. However, males with bigger combs were in better condition, had a lighter spleen, a lighter spleen than expected from their T. tenuis load and had greater cell-mediated immunity. The findings suggest that comb size relates to immune function rather than T. tenuis parasite infection intensity. Males with bigger combs are likely to be of higher phenotypic quality because they are more immunocompetent and might be better able to cope with the detrimental effects of parasites.
TL;DR: A molecular phylogeny of the major lineages of woodcreepers (Aves: Dendrocolaptinae) is presented, based on nucleotide sequence data from a nuclear non-coding gene region (myoglobin intron II) and a protein- coding mitochondrial gene (cytochrome b).
Abstract: The woodcreepers is a highly specialized lineage within the New World suboscine radiation. Most systematic studies of higher level relationships of this group rely on morphological characters, and few studies utilizing molecular data exist. In this paper, we present a molecular phylogeny of the major lineages of woodcreepers (Aves: Dendrocolaptinae), based on nucleotide sequence data from a nuclear non-coding gene region (myoglobin intron II) and a protein-coding mitochondrial gene (cytochrome b). A good topological agreement between the individual gene trees suggests that the resulting phylogeny reflects the true evolutionary history of woodcreepers well. However, the DNA-based phylogeny conflicts with the results of a parsimony analysis of morphological characters. The topological differences mainly concern the basal branches of the trees. The morphological data places the genus Drymornis in a basal position (mainly supported by characters in the hindlimb), while our data suggests it to be derived among woodcreepers. Unlike most other woodcreepers, Drymornis is ground-adapted, as are the ovenbirds. The observed morphological similarities between Drymornis and the ovenbird outgroup may thus be explained with convergence or with reversal to an ancestral state. This observation raises the question of the use of characters associated with locomotion and feeding in phylogenetic reconstruction based on parsimony.
TL;DR: The scope for water stress as an important determinant of migratory behaviour is potentially much larger than most ornithologists are inclined to believe and it is argued that the authors have been too focussed on finding birds that have been in a physiological state of dehydration, and not on behaviour directed at avoiding dehydration and optimising water balance.
Abstract: During migration, the critical costs and benefits for birds are foremost considered in terms of time, energy and predation risk (e.g. Alerstam and Lindstr6m 1990, Houston 1998). Recently, as in evolutionary ecology in general, also costs of parasitism and immune defence have been added to this list of factors that govern avian migration (Moller and Erritzoe 1998, Figuerola and Green 2000, Waldenstr6m et al. 2002). Although it was regarded as a potential danger to migrants at a relatively early stage (Yapp 1956, 1962), the potential threat of water imbalance during migration has seldom been considered a truly relevant factor that could potentially constrain a large proportion of long-distance migrants. Stimulated by this issue's publication of Sapir et al.'s (2004) study on the effect of free water on fuel-deposition rate in blackcaps Sylvia atricapilla and lesser whitethroats S. curruca in the Negev desert, I would like to briefly review the current status of Yapp's hypothesis that migrants' water budgets may constrain their migratory performance. For a bird, as for many other organisms, inadequate hydration is incompatible with life. Numerous observations exist of birds eagerly ingesting water upon arrival at a stopover site (e.g. Biebach 1990, Pennycuick et al. 1996), a phenomenon that is also well known from pigeon racing. Despite these suggestive observations and the severe consequences of dehydration, the risk of dehydration is not perceived by the majority of ornithologists to be a major and serious constraint during longdistance migration, not even when deserts or oceans have to be crossed. An important impetus for disregarding this potential constraint has been the fact that lowered body-water contents have only rarely been observed with sufficient certainty in long-distance (trans-desert) migrants (Biebach 1990, 1991, Landys et al. 2000). However, various studies on birds and mammals have shown that body water content is in fact a poor indicator of dehydration stress, since it tends to remain stable in animals dying from water restriction (Chew 1951, 1961, Dawson et al. 1979). With this important argument, on which researchers previously have refuted the possibility that a migrant's life is at least partly controlled by the risk of water imbalance (e.g. Biebach 1990, 1991, Landys et al. 2000) becomes invalid. I think that the scope for water stress as an important determinant of migratory behaviour is potentially much larger than most ornithologists are inclined to believe nd I would like to argue that we have been too focussed on finding birds that have been in a physiological state of dehydration, and not on behaviour directed at avoiding dehydration and optimising water balance. Although physiological adaptations in metabolic rate, evaporative water loss and body temperature maintenance may play a substantial role (e.g. Tieleman et al. 2003), problems of water stress in desert birds are generally thought to be solved mainly through behavioural strategies (e.g. Maclean 1996, Williams et al. 1999). If maintaining water balance was the only constraint, the three simple rules to live along in a desert are: stay out of the sun, find yourself a cool place and take it easy during the hottest parts of the day. Migrants may adopt the very same rules of thumb to avoid dehydration. During the hottest parts of the day they might for instance choose to land and find a shaded resting spot, as many birds in fact do while crossing deserts. You may find them sitting immobile in little crevasses, car tracks, or in the protection of anything else that may provide a little bit of shade. Thus, even in the absence of any direct physiological signs of dehydration, the behaviour of migrants may well be governed by the threat of dehydration. Although alternative explanations are possible (e.g. Kerlinger and Moore 1989, Schwilch et al. 2002), the landfall of many birds in the Sahara desert during daytime (Biebach 1990, Biebach et al. 1991, 2000) might be a behavioural strategy to avoid water imbalance. Using the altitudinal profiles of wind, temperature, pressure, and humidity Klaassen and Biebach (2000), and Liechti et al. (2000) tried to explain the altitudinal distributions of nocturnal migrants recorded by radar above deserts in Egypt and Israel. To this end they used
TL;DR: This work presents a probabilistic analysis of the response of the immune system to the presence of x-ray diffraction during the course of treatment of central giant coronavirus.
Abstract: is a contribution to project PB91-0081 of the Direccion General de Investigacion Cientifica y Tecnica.