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1. Frequency and types of alternative breeding strategies employed by nesting American black ducks in North Carolina

   https://doi.org/10.1371/journal.pone.0278905  

   Lavretsky, Philip; Hoyt, Amanda; Musni, Vergie M.; Howell, Doug; Williams, Christopher K. (February 2023, PLOS ONE)

   Chiang, Tzen-Yuh (Ed.)

   Although most birds are considered to be at least partially monogamous, molecular evidence continues to uncover that many species can have multiple sexual mates. Many species of Waterfowl (Order Anseriformes) consistently deploy alternative breeding strategies, and although cavity nesting species have been well studied, few attempts to understand rates of alternative breeding strategies exist in the Anatini tribe. Here, we assay mitochondrial DNA and thousands of nuclear markers across 20 broods of American black ducks ( Anas rubripes ; “black duck”) that included 19 females and 172 offspring to study population structure as well as types and rates of secondary breeding strategies in coastal North Carolina. First, we report high levels of relatedness among nesting black ducks and offspring and while 17 (of 19) females were of pure black duck descent, three were found to be black duck x mallard ( A . platyrhynchos ) hybrids. Next, we evaluated for mismatched mitochondrial DNA and paternity identities across each female’s clutch to determine types and frequency of alternative or secondary breeding strategies. Although we report that nest parasitism occurred in two nests, 37% (7 of 19) of the sampled nests were multi-paternal as a result of extra-pair copulation. In addition to being part of a mix of strategies used to increase fecundity by successfully breeding females, we posit nest densities providing easier alternative mate access for males also explains high rates of extra-pair copulation among our sampled black ducks. Ultimately, however, while some proportion of females of many species engage in forms of secondary breeding strategies, we conclude that the decision to do so appears to be seasonally flexible for each individual. 

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2. Potential drivers and implications of a balanced breeding sex ratio in a small population of an imperiled species with environmental sex determination

   https://doi.org/10.1002/ece3.70166  

   Silver‐Gorges, Ian; Shamblin, Brian_M; Ashford, Mason; Bower, Paityn; Fuentes, Mariana_M_P_B (September 2024, Ecology and Evolution)

   Abstract Small populations of imperiled species are susceptible to the negative consequences of skewed sex‐ratios. In imperiled species with environmental sex determination such as sea turtles, examining sex ratios across a range of environments and population abundance levels can provide insight into factors that influence population resilience, which can then be the foci of management plans for these species. Breeding sex ratios (the ratio of actively breeding males to females during a reproductive season; BSRs) extrapolated from genetic parentage analyses are a common approach for enumerating sex ratios in sea turtles. Such analyses also allow for the characterization of multiple paternity within sea turtle clutches, which should reflect BSRs and breeding behaviors. We characterized the first BSR for a breeding assemblage of loggerhead sea turtles (Caretta caretta) belonging to the temperate, low‐abundance Northern Gulf of Mexico Recovery Unit using genotypes of 16 microsatellite loci from nesting females and hatchlings. Unlike prior studies at both more‐tropical and more‐temperate, and higher‐abundance, Recovery Units in this region, we found a balanced BSR of 1.3:1 males:female and a low incidence (~17%) of multiple paternity. This suggests that there are relatively few males breeding at this assemblage and within this Recovery Unit. Beaches in this region are expected to produce substantial numbers of male hatchlings based on sand temperature data. The relative dearth of mature males may then be due to hydrologic disturbances that disproportionately affect the fitness and survival of male hatchlings, or due to demographic stochasticity. More work is needed to study the factors that might influence male hatchling production and fitness in this region, particularly as climate change is predicted to lead to feminization in global sea turtle populations. Our work demonstrates the broad utility of characterizing BSRs and other sex ratios across a range of populations in imperiled, environmentally sensitive species. 

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3. Female space use correlates with extra-pair mating in barn swallow replacement clutches

   https://doi.org/10.1007/s00265-025-03570-y  

   Kenny-Duddela, Heather_V; Schield, Drew_R; Keller, Kayleigh_P; Safran, Rebecca_J (February 2025, Behavioral Ecology and Sociobiology)

   Abstract Extra-pair mating is common in avian species and can modulate the strength of sexual selection. Mate searching behavior of female birds may be an important predictor of mating opportunities and extra-pair mating, yet important knowledge is lacking as we have little data on fine-scale movement of females during the peak fertilization period. Accordingly, much is still unknown about whether and how female phenotypes contribute to extra-pair mating. Here, we examined how female space use and female plumage color are associated with extra-pair mating outcomes in wild barn swallows (Hirundo rustica erythrogaster). We tracked 10 females breeding in Colorado, USA with GPS backpack tags for two hours each morning during their fertile period following an experimental nest failure. We then used low-coverage whole-genome sequencing to determine offspring paternity and to quantify extra-pair mating in the removed clutch and the replacement clutch. Plumage and movement did not correlate with changes in paternity between successive clutches, but movement did correlate with paternity in the replacement clutch. Females that spent more time away from the nest had a higher proportion and number of extra-pair offspring in the clutch laid immediately after the tracking period. These results suggest that differences in female space use contribute to differences in extra-pair fertilizations. In contrast to the historic emphasis on male traits, our study highlights female movement behavior as an important variable associated with mating outcomes in natural populations. 

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4. Modulation of Paternal Care Behaviors in Response to Stream Conditions by Eastern Hellbenders ( Cryptobranchus alleganiensis alleganiensis )

   https://doi.org/10.1093/iob/obaf007  

   O'Brien, R_S_M; Groffen, J.; Dayer, A_A; Hopkins, W_A (February 2025, Integrative Organismal Biology)

   Synopsis The rapid environmental changes associated with the Anthropocene mean that flexible behavioral responses may be a critical determinant of animals’ resiliency to anthropogenic disturbance, particularly for species with long generation times and low vagility. One type of behavior that exemplifies this potentially important flexibility is parental care. Eggs and juvenile animals are sensitive to environmental stressors, and the ability of parents to adjust care behaviors to buffer their offspring from rapidly changing conditions may be critical to successful reproduction. In this study, we explore the role of parental care in buffering eggs from anthropogenic stressors in the long-lived, fully aquatic eastern hellbender salamander (Cryptobranchus alleganiensis alleganiensis). Using custom-designed infrared cameras installed in underwater artificial shelters in a natural stream, we describe hellbender paternal care behaviors in greater detail than has previously been possible, assess the extent to which hellbender fathers buffer their eggs from increasing levels of silt and decreasing concentrations of dissolved oxygen in nesting cavities, and describe the possible trade-offs that hellbender fathers exhibit between paternal care and self-maintenance behaviors. We found that while hellbender parents buffered their offspring from low dissolved oxygen concentrations by increasing parental care, there was an apparent trade-off between parental care and self-maintenance responses to low oxygen. Hellbender fathers did not show evidence of buffering their offspring from the effects of increasing silt or organic material in their nest cavities. We also found that filial cannibalism is a widespread behavior across nests, with almost all fathers exhibiting some cannibalism, although the extent varied widely. Our study indicates that hellbender parents may be able to reduce the impacts of declines in dissolved oxygen concentration on their offspring to a limited extent, but they may be unable to fully protect offspring from increasing silt. 

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5. Maternal Responses in the Face of Infection Risk

   https://doi.org/10.1093/icb/icac082  

   Lopes, Patricia C.; Gormally, Brenna M. G.; Emmi, Aubrey; Schuerman, Delilah; Liyanage, Chathuni; Beattie, Ursula K.; Romero, L. Michael (June 2022, Integrative and Comparative Biology)

   Abstract When animals are sick, their physiology and behavior change in ways that can impact their offspring. Research is emerging showing that infection risk alone can also modify the physiology and behavior of healthy animals. If physiological responses to environments with high infection risk take place during reproduction, it is possible that they lead to maternal effects. Understanding whether and how high infection risk triggers maternal effects is important to elucidate how the impacts of infectious agents extend beyond infected individuals and how, in this way, they are even stronger evolutionary forces than already considered. Here, to evaluate the effects of infection risk on maternal responses, we exposed healthy female Japanese quail to either an immune-challenged (lipopolysaccharide [LPS] treated) mate or to a healthy (control) mate. We first assessed how females responded behaviorally to these treatments. Exposure to an immune-challenged or control male was immediately followed by exposure to a healthy male, to determine whether treatment affected paternity allocation. We predicted that females paired with immune-challenged males would avoid and show aggression towards those males, and that paternity would be skewed towards the healthy male. After mating, we collected eggs over a 5-day period. As an additional control, we collected eggs from immune-challenged females mated to healthy males. We tested eggs for fertilization status, embryo sex ratio, as well as albumen corticosterone, lysozyme activity, and ovotransferrin, and yolk antioxidant capacity. We predicted that immune-challenged females would show the strongest changes in the egg and embryo metrics, and that females exposed to immune-challenged males would show intermediate responses. Contrary to our predictions, we found no avoidance of immune-challenged males and no differences in terms of paternity allocation. Immune-challenged females laid fewer eggs, with an almost bimodal distribution of sex ratio for embryos. In this group, albumen ovotransferrin was the lowest, and yolk antioxidant capacity decreased over time, while it increased in the other treatments. No differences in albumen lysozyme were found. Both females that were immune-challenged and those exposed to immune-challenged males deposited progressively more corticosterone in their eggs over time, a pattern opposed to that shown by females exposed to control males. Our results suggest that egg-laying Japanese quail may be able to respond to infection risk, but that additional or prolonged sickness symptoms may be needed for more extensive maternal responses. 

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