Showing papers by "Point Blue Conservation Science published in 1986"

Foraging Behavior of Gentoo and Chinstrap Penguins as Determined by New Radiotelemetry Techniques

Abstract: -Analysis of radio signals from transmitters affixed to 7 Gentoo (Pygoscelis papua) and 6 Chinstrap (P. antarctica) penguins allowed us to track penguins at sea. Signal characteristics allowed us to distinguish among 5 foraging behaviors: porpoising, underwater swimming, horizontal diving, vertical diving, and resting or bathing. Gentoo Penguins spent a significantly greater portion of their foraging trips engaged in feeding behaviors than Chinstraps, which spent significantly more time traveling. Gentoos had significantly longer feeding dives than Chinstraps (128 s vs. 91 s) and significantly higher dive-pause ratios (3.4 vs. 2.6). These differences in foraging behavior suggest Gentoo and Chinstrap penguins may have different diving abilities and may forage at different depths. Received 3 June 1985, accepted 24 April 1986. THE trophic relationships among Pygoscelis penguins, the Adelie (P. adeliae), Chinstrap (P. antarctica), and Gentoo (P. papua), have been a major focal point of research in recent years, particularly with respect to the ecology of their major prey species, krill (Euphausia superba). To date, however, our knowledge of the birds' feeding ecology is largely derived from stomach samples obtained ashore (Emison 1968; Croxall and Furse 1980; Croxall and Prince 1980a; Volkman et al. 1980, 1986; Lishman 1985). Diving depth is one aspect of penguin foraging behavior that has been investigated in some detail. Multiple depth recorders, logging the number of dives within set depth ranges, have been deployed on King (Aptenodytes patagonica; Kooyman et al. 1982), Chinstrap (Lishman and Croxall 1983), and Gentoo (Costa pers. comm.) penguins. Maximum diving depths have been reported for Emperor (A. forsteri; Kooyman et al. 1971), Black-footed (Spheniscus demersus; Wilson and Bain 1984), and Gentoo (Adams and Brown 1983) penguins. Feeding range also has been investigated, but indirectly, using nest relief intervals (Williams and Siegfried 1980, Ainley et al. 1984, Croxall et al. 1984). We report a new method of tracking penguins at sea that allowed us to differentiate 1 Present address: National Marine Mammal Laboratory, NOAA/NMFS, 7600 San Point Way N.E., Seattle, Washington 98115 USA. among behaviors during foraging trips. This method improved our understanding of penguin feeding efficiencies, ranges, and traveling speeds, and permitted preliminary comparisons of Gentoo and Chinstrap penguin forag-

Antarctic mesopelagic micronekton: evidence from seabirds that pack ice affects community structure.

Abstract: Through a multidisciplinary project (AMERIEZ), with an unusual complement of components, previously unknown temporal and spatial dimensions to the structure of Antarctic epipelagic and mesopelagic communities were revealed. In late spring, an abundance of crustacean species thought to occur only below 300 meters was detected in ice-covered surface waters. Evident in ice-free waters were the expected occurrence patterns of these normally nonmigratory mesopelagic organisms. Where the pack was consolidated and little light penetrated to depth, primary and secondary production was confined to ice floes, and the physical environment immediately beneath the ice was reminiscent of a mesopelagic one. This suite of characteristics possibly explains why the crustaceans resided at the surface.

Reduced reproduction of wedge-tailed shearwaters exposed to weathered Santa Barbara crude oil

Abstract: Wedge-tailed Shearwaters breeding on Manana Island, Hawaii were treated with 0.1–2.0 ml weathered Santa Barbara crude oil either by external application to the breast plumage or by oral dose in gelatin capsules approximately 30 days prior to egg laying. Applications of oil caused reduced lay, lowered hatching success, and reduced breeding success. Two ml applied externally to the breast plumage resulted in a greatly reduced number of eggs laid and complete hatching failure of 60 pair of exposed birds. Oral doses of oil in gelatin capsules reduced laying and breeding success, but to a lesser extent than external exposure. Oil exposure did not change the length of the prelaying exodus or cause birds to move to new areas of the breeding colony, but resulted in abandonment and reduced incubation attentiveness. Growth rates of chicks of oral dosed birds were not different from controls, although survival of chicks of dosed birds was reduced. Long-term effects of external application of 2.0 ml of oil were demonstrated by a decreased number of birds returning to the colony in the year after dosing and reduced breeding success one year after oil exposure.

A Field Test of the Variable Circular-Plot Censusing Method in a Sierran Subalpine Forest Habitat

Abstract: The density and distribution of territories were determined for 21 species in a 48-ha Sierran subalpine forest study plot by an intensive program of spot-mapping and nest monitoring. About 10% of the total breeding individuals were color-banded and about 75% of the nests of all species were found. Variable circular-plot (VCP) censuses were simultaneously conducted in the same study plot. The VCP method, with minimum effort (48 stations), could describe community parameters reasonably well and could distinguish common from rare species, but could not correctly determine the relative abundances of the common species, could not correctly describe the distribution of territories within the study plot, and produced errors in density estimates for the common species that ranged from 57% to + 65%. When the effort was increased threefold (144 stations), the accuracy of the method was improved so that it produced more or less acceptable relative abundances for even the common species and was marginally capable of describing the distribution of territories for 37% of the species, particularly for those species whose distributions were markedly non-uniform, but it still produced errors in density estimates for the common species that ranged from -67% to +96%. Interestingly, VCP total count often performed nearly as well as the calculated VCP density in determining relative abundances. The accuracy of the VCP method may be expected to be poor for species with low population densities, large territory sizes, high mobilities, and ventriloqual vocalizations, and for habitats that are dense and highly three-dimensional.

Seabird Geographic Variation: Similarity Among Populations of Leach's Storm-Petrel

Abstract: -We assessed geographic variation in 13 locality samples of Leach's StormPetrel (Oceanodroma leucorhoa), 12 from the Pacific coast and 1 from the Atlantic coast of North America. Nine phenetic characters were used with canonical variates analysis to determine similarity among samples. Regression of phenetic distance on geographic distance measured the relation between similarity and interisland distance. We found a clinal pattern of population similarity from the Aleutian Islands in the north to the Farallon Islands in the south. Populations from Los Coronados and San Benitos islands make up a distinct subset when rump color and wing and tail shape indices are included in the analysis, but these populations were part of a dominant clinal trend when only five size characters were used. On Guadalupe Island separate populations breed in summer and winter; these are strongly differentiated from the others and from each other. The North Atlantic sample was aligned closely with that from the Aleutians. The degree of geographic variation was roughly similar to that in certain migratory land birds on the North American continent, but is less than what is found for certain nonmigratory land birds on islands. Our results suggest recognizing four subspecies of Leach's Storm-Petrel in the study area, including two on Guadalupe Island isolated by time of breeding. Received 7 May 1984, accepted 3 March 1986. SEABIRDS often range over wide areas, yet return to specific island sites to reproduce. As a result, the breeding populations of many pelagic species are isolated geographically (King 1974). It is not known if the degree of reproductive isolation and the concomitant potential for divergence of island-breeding seabird populations are any greater than what might be found in land birds. A comparable mainland situation might be a migratory species with populations that nest in isolated habitat "islands." The interrupted breeding distribution of seabirds offers an attractive situation for study of geographic variation. Seabirds, however, have not figured prominently in our understanding of intraspecific evolution; most information on avian geographic variation comes from studies of land birds (e.g. Selander 1971). In a univariate analysis of geographic variation on breeding populations of Leach's StormPetrel (Oceanodroma leucorhoa) in the eastern North Pacific and the western North Atlantic oceans, Ainley (1980) found that several characters vary clinally from the Aleutian Islands in the north to the San Benitos Islands off the west coast of Baja California, Mexico. In addition, the fact that Guadalupe Island supports two morphologically distinct populations, one breeding in summer and the other in winter, led Ainley to describe the winter population as a new race. Bourne and Jehl (1982) criticized some of Ainley's interpretations (see also Ainley 1983 and Jehl and Everett 1985). We reanalyzed the morphological data by combining characters in a multivariate analysis. Information Ainley presented on vocalizations was not considered. We examined the pattern of overall similarity among populations of Leach's StormPetrel and the relationship between specific island colonies, aspects of geographic variation that were difficult to assess only through variation in single characters. We also measured the relationship between overall similarity and interisland distance to see if the pattern of geographic variation is a function of geographic distance, as is often the case with land birds.

Metabolism, Growth, and Activity in Adélie and Emperor Penguin Embryos

Abstract: The eggs of Adelie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) penguins are smaller than those of large species in other orders. The incubation period in Adelie Penguins was as predicted based on egg mass, but in Emperor Penguins it was 50% longer than predicted. Although penguins have been described as semialtricial using the behavioral and morphological traits in Nice's (1962) classification, total oxygen consumption during incubation was similar to that of eggs of the same masses laid by precocial species. In both penguin species prepipping oxygen consumption was at a level predicted for precocial species. Adelie embryos grew continuously during the last two weeks of incubation, but the relative growth rate (%/day) of both wet and dry mass decreased steadily until day 32 of incubation. From day 21 to day 31 of incubation, there was no significant change in the wet mass, dry mass, or caloric content of yolk. The mass-specific caloric content of the embryos remained constant at 5.49 kcal/g dry mass. Activity of the embryo between pipping and hatching contributed importantly to measured oxygen consumption (10% of the total measured during incubation, -20% in pipped eggs from 3 days to 1 day before hatching, and -25% on the day of hatching). We suggest that the limited behavioral repertoire of hatchling penguins evolved as a response to the severity of the environment into which they hatch and because of the skilled predatory behavior that they must learn before they can feed themselves. Received 21 June 1985, accepted 6 January 1986. MANY investigators have measured the energy metabolism of avian embryos and discussed the empirical relationships between this and other functions, including embryonic growth, egg mass at laying, length of incubation, developmental type at hatching, adult mass, adult basal metabolic rate, and conductance of the eggshell (for recent reviews and discussions see C. Vleck et al. 1980, Rahn 1982, Bucher and Bartholomew 1984). A stated or an implicit assumption in most of these studies is that the contribution of activity to the total energy metabolism of avian embryos is minimal. Embryonic oxygen consumption usually has been measured in closed respirometry systems, except for very large eggs (D. Vleck et al. 1980) and in a few recent studies (e.g. Bartholomew and Goldstein 1984). Closed-system respirometry is integrative and gives only average values and rates of energy metabolism over relatively extended time periods. Recently, it has become possible to follow short-term fluctuations in energy metabolism by using flow-through respirometry and calculating instantaneous rates of oxygen consumption (Bartholomew et al. 1981). Continuous monitoring of rates of oxygen consumption of avian embryos over extended periods of time allows one to determine short-term variability in oxygen consumption of an individual due to activity as well as variation due to longer-term ontogenetic change. All members of the order Sphenisciformes are considered to be semialtricial (Nice 1962). Most lay their eggs in relatively to extremely cold environments characterized by low absolute humidity. Emperor (Aptenodytes forsteri) and Adelie (Pygoscelis adeliae) penguins breed on the Antarctic continent and its fringe islands and have a circumpolar distribution. There were no published data on embryonic growth and metabolism in penguins, so it was necessary to establish as broad a data base as possible from the combination of materials available to us (see Methods). We collected Adelie Penguin eggs of known age from colonies near Arctowski Station and Palmer Station in the Antarctic. We made physiological measurements on the eggs of Emperor Penguins and on the eggs and chicks of Adelie 485 The Auk 103: 485-493. July 1986 This content downloaded from 157.55.39.132 on Thu, 15 Sep 2016 06:17:50 UTC All use subject to http://about.jstor.org/terms 486 BUCHER ET AL. [Auk, Vol. 103 Penguins at Sea World in San Diego, California. Measurements of embryonic mass and accompanying yolk mass were obtained when possible to allow analysis of growth patterns and of energy allocation at specific times during incubation.