David Winkler - Academia.edu (original) (raw)

Papers by David Winkler

Volume 8: Energy Systems: Analysis, Thermodynamics and Sustainability; Sustainable Products and Processes, 2008

Wildlife monitoring tags are a widely used technique for studying animals in their natural habita... more Wildlife monitoring tags are a widely used technique for studying animals in their natural habitats. At present, these devices are energy limited, based on the mass of the electrochemical battery that can be carried by the animal. Flying animals are particularly restricted, based on a requirement for minimal excess loading. This requirement causes tag lifetimes to be far shorter than would be useful from an ecological perspective, particularly for smaller animals. Energy harvesting is being widely adopted in applications where access to permanent power is limited. If applied to wildlife tags, this approach offers the possibility of extending functional lifetimes indefinitely; however, it presents unique challenges. Practical applications on flying animals are extremely mass limited, subject to environmental stress, and operate at very low frequencies. This paper is meant to address the critical issues in the design task, and makes attempts to place bounds on unknown design parameter...

Emu - Austral Ornithology, 2015

Intermittent female incubation, where eggs are left unattended periodically while the female fora... more Intermittent female incubation, where eggs are left unattended periodically while the female forages, is common among passerines. In extremely cold environments, unattended eggs may be at risk of freezing or exposed to suboptimal developmental temperatures. Our aim was to examine incubation behaviour of Chilean Swallows nesting in a cold environment (daily average temperatures~10 C) at the southern tip of Argentina, and the temperature regime of incubation. Females had bare, vascularised brood-patches, whereas males had false brood-patches, where feathering of the abdomen was somewhat sparse. Video-cameras were used at three nests, and at all three two adults were observed to attend eggs, day and night, confirming incubation by males. Temperature records of eggs showed that one adult (assumed to be the female) had high rates of attendance and maintained egg temperatures that approached 38À39 C when incubating, and the other adult (assumed male) had lower and variable rates of attendance and maintained egg temperatures generally above 34 C when incubating. The assumed female rarely left the eggs unless the assumed male was there to replace her. Researchers should be cautious when making conclusions using data from temperature loggers in situations where male attendance at nests during incubation is possible.

Science, 2008

The cues used by birds and other species to trigger reproduction determine how successfully they ... more The cues used by birds and other species to trigger reproduction determine how successfully they can respond to climate change.

Proceedings of the Royal Society of London. Series B: Biological Sciences, 1999

Increasing evidence suggests that climate change has a¡ected the breeding and distribution of wil... more Increasing evidence suggests that climate change has a¡ected the breeding and distribution of wildlife. If such changes are due to global warming, then we should expect to see large-scale e¡ects. To explore for such e¡ects on avian reproduction, we examined 3450 nest records of tree swallows from across North America. The egg-laying date in tree swallows advanced by up to nine days during 1959^1991. This advance in phenology was associated with increasing surface air temperatures at the time of breeding. Our analysis controlled for several potentially confounding variables such as latitude, longitude, breeding density and elevation. We conclude that tree swallows across North America are breeding earlier and that the most likely cause is a long-term increase in spring temperature.

Molecular Phylogenetics and Evolution, 2012

The Tachycineta genus of swallows is comprised of nine species that range from Alaska to southern... more The Tachycineta genus of swallows is comprised of nine species that range from Alaska to southern Chile. We sequenced the entire mitochondrial genome of each member of Tachycineta and generated a completely resolved phylogenetic hypothesis for the corresponding mitochondrial gene tree. Our analyses confirm the presence of two sub-clades within Tachycineta that are associated with geography: a North American/Caribbean clade and a South/Central American clade. We found considerable variation among regions of the mitochondrial genome in both substitution rates and the level of information that each region supplied for phylogenetic reconstruction. We found no evidence of positive directional selection within mitochondrial coding regions, but we identified numerous sites under purifying selection. This finding suggests that, despite differences in life history traits and distributions, mitochondrial genes in Tachycineta are predominantly under purifying selection for conserved function.

Ibis, 2008

Nestling growth rates make an excellent indicator of the effects of environmental variation on fi... more Nestling growth rates make an excellent indicator of the effects of environmental variation on fitnes, because growth varies on a temporal scale similar to the scale of variability in weather patterns and becauw growth is a good indicator of subsequent survival and reproductive success (

Functional Ecology, 2012

1. Birds often lose body mass during nesting. Determining whether this mass loss represents an en... more 1. Birds often lose body mass during nesting. Determining whether this mass loss represents an energetic cost of reproduction (energetic stress hypothesis), serves an adaptive function (flight efficiency hypothesis), or results from physiological processes that are neutral with respect to fitness (e.g. gonadal regression hypothesis) is important to interpreting variation in body mass and energy stores in the context of life-history theory. 2. New quantitative magnetic resonance technology enables precise, repeated measurements of body composition (fat, lean, and water masses) on the same individuals, and we used this method to test a series of predictions to distinguish among competing hypotheses explaining mass loss in female tree swallows (Tachycineta bicolor, Vieillot, 1808). 3. Tree swallows lost mass abruptly prior to the peak foraging demands of feeding chicks. Lean mass and fat mass losses varied independently, with small and gradual losses in lean mass during incubation and dramatic losses of fat immediately prior to and following hatching. Females lost some body water early in incubation, but did not lose more water when brood patches would be expected to atrophy. The period of greatest parental foraging costs was not associated with any significant changes in total body mass, lean mass, fat mass or water. Net change in body mass from early incubation until midway through chick rearing was associated strongly with initial body mass and to a lesser degree, brood size. 4. These findings are consistent with the flight efficiency hypothesis. Females appear to facultatively modulate their endogenous energy stores to maximize insurance against bad weather and poor foraging opportunities during incubation, but then lower their body mass to maximize efficiency once chicks hatch, thereby reducing the costs of feeding nestlings. 5. This study corroborates results of a growing number of studies of small, insectivorous birds (especially cavity-nesting species), suggesting that increases in mass prior to reproduction (and the subsequent loss of that mass) are likely best viewed as part of an adaptive suite of interrelated reproductive decisions made by females each year.

Ecology, 2011

In seasonal environments, vertebrates are generally thought to time their reproduction so offspri... more In seasonal environments, vertebrates are generally thought to time their reproduction so offspring are raised during the peak of food abundance. The mismatch hypothesis predicts that reproductive success is maximized when animals synchronize their reproduction with the food supply. Understanding the mechanisms influencing the timing of reproduction has taken on new urgency as climate change is altering environmental conditions during reproduction, and there is concern that species will not be able to synchronize their reproduction with changing food supplies. Using data from five sites over 24 years (37 siteyears), we tested the assumptions of the mismatch hypothesis in the Tree Swallow (Tachycineta bicolor), a widespread aerial insectivore, whose timing of egg-laying has shifted earlier by nine days since the 1950s. Contrary to the mismatch hypothesis, the start of egglaying was strongly related to food abundance (flying insect biomass) during the laying period and not to timing of the seasonal peak in food supply. In fact, food abundance generally continued to increase throughout the breeding season, and there was no evidence of selection based on the mistiming of laying with the seasonal peak of food abundance. In contrast, there was selection for laying earlier, because birds that lay earlier generally have larger clutches and fledge more young. Overall, initial reproductive decisions in this insectivore appear to be based on the food supply during egg formation and not the nestling period. Thus, the mismatch hypothesis may not apply in environments with relatively constant or abundant food throughout the breeding season. Although climate change is often associated with earlier reproduction, our results caution that it is not necessarily driven by selection for synchronized reproduction.

Ecological Applications, 2010

The distributions of animal populations change and evolve through time. Migratory species exploit... more The distributions of animal populations change and evolve through time. Migratory species exploit different habitats at different times of the year. Biotic and abiotic features that determine where a species lives vary due to natural and anthropogenic factors. This spatiotemporal variation needs to be accounted for in any modeling of species' distributions. In this paper we introduce a semiparametric model that provides a flexible framework for analyzing dynamic patterns of species occurrence and abundance from broadscale survey data. The spatiotemporal exploratory model (STEM) adds essential spatiotemporal structure to existing techniques for developing species distribution models through a simple parametric structure without requiring a detailed understanding of the underlying dynamic processes. STEMs use a multi-scale strategy to differentiate between local and globalscale spatiotemporal structure. A user-specified species distribution model accounts for spatial and temporal patterning at the local level. These local patterns are then allowed to ''scale up'' via ensemble averaging to larger scales. This makes STEMs especially well suited for exploring distributional dynamics arising from a variety of processes. Using data from eBird, an online citizen science bird-monitoring project, we demonstrate that monthly changes in distribution of a migratory species, the Tree Swallow (Tachycineta bicolor), can be more accurately described with a STEM than a conventional bagged decision tree model in which spatiotemporal structure has not been imposed. We also demonstrate that there is no loss of model predictive power when a STEM is used to describe a spatiotemporal distribution with very little spatiotemporal variation; the distribution of a nonmigratory species, the Northern Cardinal (Cardinalis cardinalis).

The Condor, 1999

... JOHN P. MCCARTY2 AND DAVID W. WINKLER Section of Ecology and Systematics, Division of Biologi... more ... JOHN P. MCCARTY2 AND DAVID W. WINKLER Section of Ecology and Systematics, Division of Biological Sciences, Corson Hall, Cornell University, Ithaca, NY ... 1992, McCarty 1995), making an understanding of foraging critical to understand-ing their ecology as a whole. ...

The Condor, 2004

To study the patterns and determinants of philopatry and breeding dispersal in the Tree Swallow (... more To study the patterns and determinants of philopatry and breeding dispersal in the Tree Swallow (Tachycineta bicolor) we analyzed the records of 356 males and 1459 females captured in more than one breeding year around Ithaca, New York. Of these captures, only 4% of male and 14% of female breeders dispersed to a new site for breeding. With our combination of intensive study areas in Tompkins County, New York, and the efforts of volunteer banders throughout New York and surrounding states, we could have detected dispersal in excess of 400 km from the initial breeding site. Randomization tests revealed, however, that breeders dispersed much shorter distances than they could have been detected. Detailed analyses of recaptures in Tompkins County showed that over a 22-km range of distances, the chances of dispersal to a new breeding site declined with the distance from the original breeding site. Females that failed to fledge any offspring were much more likely to disperse than females that reproduced successfully, and the probability of dispersal declined gradually with female age. The spatial scale in which swallows gather and process information appears to be much larger than for passerines that defend all-purpose territories.

The Condor, 2000

In recent years, two approaches have emerged for the analysis of character evolution: the largely... more In recent years, two approaches have emerged for the analysis of character evolution: the largely statistical ''convergence'' approach and the mainly cladistic ''homology'' approach. I discuss the strengths and weaknesses of these approaches as they apply to phylogenetic analyses of life-history variation in birds. Using examples from analyses of character variation in swallows, I suggest that the phylogenetic approach yields distinctive insights into the selective role of the environment and other characters of the organism on the evolution of life-history traits. This view thus has the potential of bringing together micro-and macro-evolutionary views of life-history evolution.

Bulletin of Mathematical Biology, 1992

... 0092 8240/9255.00-t-0.00 Pergamon Press plc 1991 Society for Mathematical Biology HUNGRY CHIC... more ... 0092 8240/9255.00-t-0.00 Pergamon Press plc 1991 Society for Mathematical Biology HUNGRY CHICKS AND MORTAL PARENTS: A STATE-VARIABLE ... number of offspring in all our experimental runs, and in most, this increase reaches a plateau at eight or nine offspring (Fig ...

Biochemical Systematics and Ecology, 1983

California Gulls nesting at Mono Lake (ML) have a modal clutch size of two eggs, while at Great S... more California Gulls nesting at Mono Lake (ML) have a modal clutch size of two eggs, while at Great Salt Lake (GSL) the mode is three. We used starch gel electrophoresis to determine whether the populations are genically different. Average individual heterozygosity at ML averages 2.67% and at GSL 2.95%, both slightly below the average for other birds. The average number of alleles per locus is 1.2 for both sites. Variation between sites is insignificant, with a genetic distance of 0.001 and an FST of 0.0044. Therefore, the clutch size differences are without genic correlates. In fact, at the loci studied, the two samples are indistinguishable from two random samples drawn from a panmictic unit. Five morphological characteristics also exhibited little between-site difference, in agreement with the electrophoretic analysis. A marked historical reduction (bottleneck) in the Mono Lake population seems not to have affected levels of genetic variation. We conclude that the clutch size differences are either recently evolved, and determined by loci not surveyed by us, or they are environmentally induced. At the population level, these gulls are similar to passerines in terms of heterozygosity and among-population differentiation.

Behavioral Ecology, 2006

Nestling begging in the absence of parents may reflect ''false alarms'' due to cognitive constrai... more Nestling begging in the absence of parents may reflect ''false alarms'' due to cognitive constraints or signaling activity toward nest mates (sibling negotiation). According to signal detection theory, cognitive constraints should result in both false alarms (begging in the absence of parents or to inappropriate stimuli) and misses (failure to beg during parental visits). In our study of house sparrows, nestling begging in the absence of parents comprised up to 50% of the begging events at the nest and was more frequent at an early age and among hungrier (lower ranked) nestlings. In contrast, the probability of begging during parental visits was constantly high (80% or more), suggesting that the rate of misses must have been low even at an early age. These results have 2 main implications. First, the observation that begging in the absence of parents decreases with nestling age favors the cognitive constraints hypothesis over functional explanations such as the sibling negotiation hypothesis. Second, the low proportion of ''misses'' among young nestlings suggests that nestling respond to their cognitive constraints by using low decision criteria (a ''quick on the trigger'' strategy) that increases the frequency of false alarms but minimizes costly misses.

Behavioral and Brain Sciences, 2004

We welcome Soltis' use of evolutionary signaling theory, but question his interpretations of ... more We welcome Soltis' use of evolutionary signaling theory, but question his interpretations of colic as a signal of vigor and his explanation of abnormal high-pitched crying as a signal of poor infant quality. Instead, we suggest that these phenomena may be suboptimal by-products of a generally adaptive learning process by which infants adjust their crying levels in relation to parental responsiveness.

The Auk, 1993

The phylogeny of the subfamily Hirundininae was estimated by hybridizing single-copy nuclear DNAs... more The phylogeny of the subfamily Hirundininae was estimated by hybridizing single-copy nuclear DNAs of 21 swallow species, representing 19 former and current genera, and a Tufted Titmouse (Parus bicolor) as outgroup. The phylogeny, which was unusually well resolved, consisted of three fundamental clades: Hirundo and allies, core martins, and African sawwings. The clade of Hirundo and allies comprised Hirundo rustica, Ptyonoprogne fuligula, Delichon urbica, Cecropis semirufa, Petrochelidon pyrrhonota, and P. spilodera. The sister-group of Hirundo and allies was the core martin clade, which consisted largely of endemic New World taxa (Pygochelidon cyanoleuca, Neochelidon tibialis, Atticora fasciata, Phaeoprogne tapera, Progne chalybea, Haplochelidon andecola, Stelgidopteryx ruficollis, and Tachycineta bicolor) and some basally branching Old World groups (Riparia riparia, R. cincta, Phedina borbonica, Pseudhirundo griseopyga, and Cheramoeca leucosternus). The African sawwings (represented by Psalidoprocne holomelas) formed the sister group of the core martins and Hirundo and allies. Among some interesting discoveries, we found a close relationship between the monotypic African and Australian genera Pseudhirundo and Cheramoeca. We also found that Delichon, which has persisted in the nomenclature as a genus separate from Hirundo, is monophyletic with taxa that are commonly considered to be members of Hirundo. On the other hand, Haplochelidon andecola, which is often considered to be a Hirundo or Petrochelidon, is not closely related to those genera, but instead lies among the New World members of the core martin clade.