Biology subjects

Welklin, J. F.

Publications and source records attributed to Welklin, J. F..

5 recordsLinked to original sources

bioRxiv2026

Drought to deluge: Differential impacts of snow on mountain chickadee reproduction across the Sierra Nevada mountains

Changing climates are reshaping animal populations, but our understanding of how demographic trends are shaped by individual responses to local environmental conditions has historically been limited to long-term studies with restricted spatial scales. Participatory science (i.e. citizen science) programs have improved our ability to identify geographic variation in population-level trends, but these programs often lack insight into the individual-level processes that underly such variation. Here we present a new research framework that uses long-term data to validate participatory science observations as measurements of reproductive success, then explores reproductive responses to environmental variation across large geographic scales. We use this approach to investigate how reproduction in a montane songbird, the mountain chickadee (Poecile gambeli), varies in response to extreme scarcity and extreme accumulation of snow throughout the Sierra Nevada Mountains in North America. Reproductive responses to snowfall extremes varied considerably across elevations and latitudes. In the northern Sierra Nevada, mountain chickadee reproductive performance was negatively affected by snow deluge conditions at high elevations, whereas snow drought conditions reduced reproductive output at low elevations. In the central Sierras, drought conditions negatively impacted both elevations, but deluge conditions improved reproductive performance at both low and high elevations. Reproduction in the southern Sierra Nevada was nearly unaffected by spring snow levels. These variable responses to extreme snow accumulation across environments corroborate increasing evidence that biological responses to environmental variation are often nonstationary across spatial scales. Our results show that long-term studies can be used to inform and interpret participatory science data to provide a framework that strengthens our understanding of how individual behaviors underly differential responses to environmental variation across geographic scales.

ecology↗

bioRxiv2025

Seeking smarts: Male chickadees with better spatial cognition sire more extra-pair young

Across animal taxa, females commonly mate with more than one male, even in monogamous mating systems. These extra-pair (EP) copulations and resulting young may increase the fitness of the female via a variety of mechanisms. The "good genes" hypothesis suggests that socially monogamous females mate outside their pair bond to increase the fitness of their offspring via indirect genetic benefits, because extra-pair males do not provide parental care. We tested this hypothesis by quantifying extra-pair paternity in nonmigratory, food-caching mountain chickadees (Poecile gambeli). Chickadees rely on spatial cognition to recover scattered food caches and variation in spatial cognition is associated with increased survival, longer lifespan, and is heritable. However, less is known about the role of sexual selection on spatial cognitive abilities. In the current study, we found that 1. males with better spatial cognitive abilities sired more extra-pair young and produce heavier offspring in their own nests compared to their poorer performing counterparts, and 2. extra-pair males had significantly better spatial cognition than the social males they cuckolded. These results suggest that sexual selection shapes the evolution of spatial cognition in food-caching chickadees and are consistent with the good genes hypothesis, which posits that females gain indirect genetic benefits via extra-pair young.

animal behavior and cognition↗

bioRxiv2023

Plural breeding among unrelated females and other insights on complex social structure in the cooperatively breeding Variegated Fairywren

Cooperatively breeding species vary widely in degree of social complexity, and disentangling relationships among group members can reveal the costs and benefits of cooperation. Here, we explore the social system of a relatively unstudied cooperatively breeding bird, the Variegated Fairywren (Malurus lamberti), and explore how social complexity and group dynamics may affect cooperation and conflict. We used a combination of field-based population monitoring and detailed social association observations to determine group membership annually across four breeding seasons (2014 - 2017), and used a ddRAD-seq genotyping method to determine genetic relationships within social groups. Social groups ranged in size from 2 - 8 individuals and nearly half of all social groups had multiple adult individuals of both sexes. Approximately two-thirds of those groups exhibited plural breeding, in which multiple females within the same social group nested individually on the same territory. Genetic relationships were diverse across social groups, and many consisted of a combination of relatives and non-relatives of each sex. Notably, although related females often were present within a social group, co-breeding females in the same social group were never closely related to each other. Given extensive variation in relatedness among group members, cooperation in the Variegated Fairywren is likely maintained by a combination of direct and indirect fitness benefits.

ecology↗

bioRxiv2022

Unexpected long-term retention of subcutaneous beeswax implants and additional notes on dose and composition from four testosterone implant studies

Experimental manipulations of testosterone have advanced our understanding of the hormonal control of traits across vertebrates. Implants are commonly used to supplement testosterone and other hormones to organisms, as they can be readily scaled to produce desired hormone levels in circulation. Concerns about pharmacological (i.e. unnatural) doses of traditional silastic implants led to innovation in implant methods, with time-release pellets and beeswax implants proposed as solutions. A study comparing silastic, time-release pellets, and beeswax implants found the latter to be most effective in delivering a physiologically relevant dose. One proposed advantage to subcutaneous beeswax implants is that they are expected to degrade within the body, thus removing the obligation to recapture implanted individuals in the field. However, few studies have reported on dosage and no published literature has examined the assumption that beeswax implants readily degrade as expected. Here we present time-release androgen data in relation to implants containing varying levels of testosterone from four separate implant studies. In addition, we report long-term persistence of subcutaneous implants, including two cases of implants being retained for > 2 years. Finally, we offer recommendations on the composition and implementation of beeswax implants to aid the pursuit of minimally invasive and physiologically relevant manipulations of circulating hormones.

animal behavior and cognition↗

bioRxiv2021

Male White-shouldered Fairywrens (Malurus alboscapulatus) elevate testosterone when courting females but not during territorial challenges

Testosterone mediates suites of physical and behavioral traits across vertebrates, and circulation varies considerably across and within taxa. However, an understanding of the causal factors of variation in circulating testosterone has proven difficult despite decades of research. According to the challenge hypothesis, agonistic interactions between males immediately prior to the breeding season produce the highest levels of testosterone measured during this period. While many studies have provided support for this hypothesis, most species do not respond to male-male competition by elevating testosterone. As a result, a recent revision of the hypothesis ( challenge hypothesis 2.0) places male-female interactions as the primary cause of rapid elevations in testosterone circulation in male vertebrates. Here, we offer a test of both iterations of the challenge hypothesis in a tropical bird species. We first illustrate that male White-shouldered Fairywrens (Malurus alboscapulatus) differ by subspecies in plasma testosterone concentrations. Then we use a social network approach to find that males of the subspecies with higher testosterone are characterized by greater social interaction scores, including more time aggregating to perform sexual displays. Next, we use a controlled experiment to test whether males respond to simulated territorial intrusion or courtship interaction contexts by elevating testosterone. Males sampled during courtship had greater plasma testosterone both relative to flushed controls and males sampled during simulated intrusion. Ultimately, our results are consistent with challenge hypothesis 2.0, as males rapidly elevated testosterone following interactions with females, but not during territorial challenges.

animal behavior and cognition↗