Statistics for Spatial Data.

Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

A DNA test to sex most birds.

Animals have evolved limb proportions adapted to different environments, but it is not yet clear to what extent these proportions are directly influenced by the environment during prenatal development. The developing skeleton experiences mechanical loading resulting from embryo movement. We tested the hypothesis that environmentally-induced changes in prenatal movement influence embryonic limb growth to alter proportions. We show that incubation temperature influences motility and limb bone growth in West African Dwarf crocodiles, producing altered limb proportions which may, influence post-hatching performance. Pharmacological immobilisation of embryonic chickens revealed that altered motility, independent of temperature, may underpin this growth regulation. Use of the chick also allowed us to merge histological, immunochemical and cell proliferation labelling studies to evaluate changes in growth plate organisation, and unbiased array profiling to identify specific cellular and transcriptional targets of embryo movement. This disclosed that movement alters limb proportions and regulates chondrocyte proliferation in only specific growth plates. This selective targeting is related to intrinsic mTOR (mechanistic target of rapamycin) pathway activity in individual growth plates. Our findings provide new insights into how environmental factors can be integrated to influence cellular activity in growing bones and ultimately gross limb morphology, to generate phenotypic variation during prenatal development.

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Limb proportions show developmental plasticity in response to embryo movement.

A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that temperate taxa are often younger than, and nested within, tropical taxa, and that diversity is positively correlated with the age and area of geographical regions. The diversification rate hypothesis holds that tropical regions diversify faster due to higher rates of speciation (caused by increased opportunities for the evolution of reproductive isolation, or faster molecular evolution, or the increased importance of biotic interactions), or due to lower extinction rates. There is phylogenetic evidence for higher rates of diversification in tropical clades, and palaeontological data demonstrate higher rates of origination for tropical taxa, but mixed evidence for latitudinal differences in extinction rates. Studies of latitudinal variation in incipient speciation also suggest faster speciation in the tropics. Distinguishing the roles of history, speciation and extinction in the origin of the latitudinal gradient represents a major challenge to future research.

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Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography

Incubation behavior is one component of reproductive effort and thus influences the evolution of life-history strategies. We examined the relative importance of body mass, frequency of mate feeding, food, nest predation, and ambient temperature to explain interspecific variation in incubation behavior (nest attentiveness, on- and off-bout durations, and nest trips per hour) using comparative analyses for North American passerines in which only females incubate. Body mass and frequency of mate feeding explained little variation in incubation behavior. We were also unable to detect any influence of food; diet and foraging strategy explained little interspecific variation in incubation behavior. However, the typical temperature encountered during reproduction explained significant variation in incubation behavior: Species breeding in colder environments take shorter bouts off the nest, which prevents eggs from cooling to temperatures below the physiological zero temperature. These species must compe...

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.0014-3820.2000.tb00068.x

Evolution of passerine incubation behavior: influence of food, temperature, and nest predation.

Ambient temperature is commonly thought to influence avian incubation behavior. However, results of empirical studies examining correlations between ambient temperature and bout duration are equivocal. We propose that these equivocal results can be partly explained by developing a conceptual understanding of how we should expect temperature to influence incubation. We demonstrate why linear correlation analyses across a wide range of temperatures can be inappropriate based on development of an incubation model for small birds that incorporates how ambient temperature influences both embryonic development and adult metabolism. We found support for predictions of the model using incubation data from orange-crowned warblers (Vermivora celata) in Arizona. Both off- and on-bout duration were positively correlated with ambient temperature between 9 and 26C, but unrelated to ambient temperature 9 and 26–40C. Bout durations declined as ambient temperature approached or exceeded 40C. Incubating orange-crowned warblers appeared to avoid bouts off the nest 7 min and bouts on the nest 20 min. Time of day, duration of the previous bout, and variation among nests all explained variation in both onand off-bout duration. Although we found support for the general shape of the incubation model, temperature still explained only a small portion of the overall variation in on- and off-bout duration. Results of previous studies were generally consistent with the model for off-bout duration; most studies in colder environments reported positive correlations with temperature, and the one negative correlation reported was from a hot environment. However, the relationships between on-bout duration and temperature reported in previous studies were less consistent with our model and our data. Although some discrepancies could be explained by considering our model, some studies reported negative correlations in cold environments. The effect of ambient temperature on duration of on-bouts probably differs among species based on the amount of fat reserves females typically carry during incubation and the extent of male incubation feeding. Additional studies of the effects of temperature on avian incubation will help improve the general model and ultimately aid our understanding of energetic and ecological constraints on avian incubation. Key words: ambient temperature, foraging, incubation behavior, incubation model, incubation rhythm, nest attentiveness, on-bout duration, off-bout duration. [Behav Ecol 11:178–188 (2000)]

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Effects of ambient temperature on avian incubation behavior

. Little is known about the population status of many marsh-dependent birds in North America but recent efforts have focused on collecting more reliable information and estimates of population trends. As part of that effort, a standardized survey protocol was developed in 1999 that provided guidance for conducting marsh bird surveys throughout North America such that data would be consistent among locations. The original survey protocol has been revised to provide greater clarification on many issues as the number of individuals using the protocol has grown. The Standardized North American Marsh Bird Monitoring Protocol instructs surveyors to conduct an initial 5-minute passive point-count survey followed by a series of 1-minute segments during which marsh bird calls are broadcast into the marsh following a standardized approach. Surveyors are instructed to record each individual bird from the suite of 26 focal species that are present in their local area on separate lines of a datasheet and estim...

/pdf/standardized-north-american-marsh-bird-monitoring-protocol-4m6fbtug9y.pdf

Standardized North American Marsh Bird Monitoring Protocol

Many species of marsh birds (e.g. rails and bitterns) are believed to be declining in North America, yet we lack an effective monitoring program to estimate their population trends. Broadcast of prerecorded calls to elicit vocalizations is a commonly used method in surveys of marsh birds, but whether gains in detection and index precision outweigh the drawbacks of call-broadcast is unclear. To evaluate the effectiveness of call-broadcast surveys, we pooled marsh-bird survey data from 8,047 point-count surveys contributed by 11 cooperators and compared numbers of birds detected and variation in numbers detected between call-broadcast and passive surveys. For most rails (particularly Virginia Rails [Rallus limicola]), call-broadcast surveys were effective at increasing the detection probability (e.g. average number of Virginia Rails detected per occupied point was 1.25 for call-broadcast surveys and 0.17 for passive surveys). The proportion of points at which no birds were detected was high for all...

Effectiveness of call-broadcast surveys for monitoring marsh birds

Populations of western burrowing owls (Athene cunicularia hypugaea) appear to have declined in many portions of their range. A standardized survey and monitoring program is not available to quantify changes in abundance or distribution. Before a standardized survey method is selected for long-term, continent-wide burrowing owl monitoring, potential survey protocols should be rigorously tested. We evaluated 3 potential burrowing owl survey methods: line transect, roadside point-count, and driving surveys. We also examined the effectiveness of using call-broadcasts on point-count surveys to increase detection probability. We conducted 3 replicate borrowing owl surveys (either point-count or driving surveys) along 1,350 km of roads (114 survey routes) in eastern Wyoming, USA, between June and August 2000. Detection probability varied among observers for both point-count and driving surveys. Detection probability was higher on point-count, surveys (x = 64.3%) compared to driving surveys (x = 37.5%), and point-count surveys sampled a larger effective area away from the road. Walking line-transect surveys proved ineffective and inefficient for monitoring burrowing owls at large (statewide) scales. Nest-site detection probability was 47% during driving detection trials and 79% during point-count detection trials. We detected over twice as manly owls per unit distance on our point-count routes (0.038 owls/km) compared to our driving routes (0.016 owls/km), but detected more owls per unit time on our driving routes (0.339 owls/hr vs. 0.229 owls/hr on point-count routes). We detected 22% more owls using call-broadcast even though all of our detections on pointcount surveys were visual rather that aural. Estimates of breeding density were fairly similar based on our driving and point-count surveys (0.110 and 0.074 nest sites/km 2 , respectively). Standardized point-counts using call-broadcast along roadsides offer the best approach for monitoring population trends of burrowing owls at large (statewide) spatial scales. Based on our results, we developed a standardized survey protocol for monitoring burrowing owls at large spatial scales. Implementation of these monitoring protocols would provide more precise estimates of population trends of burrowing owls in North America.

Courtney J. Conway

Papers

Evolution of passerine incubation behavior: influence of food, temperature, and nest predation.

Effects of ambient temperature on avian incubation behavior

Standardized North American Marsh Bird Monitoring Protocol

Effectiveness of call-broadcast surveys for monitoring marsh birds

Comparison of detection probability associated with burrowing owl survey methods