Demographic data on avian species are critically important for conservation and management. Research on avian demography often requires some level of human disturbance at nest sites. We document researcher disturbance influence on Double-crested Cormorant (<em>Nannopterum auritum</em>: cormorant) reproductive parameters of nest success and survival at breeding colonies on Spider and Pilot Islands, Lake Michigan, Wisconsin, USA. Cormorant nests were monitored daily throughout the breeding season (April–August) via game cameras. Breeding colonies were subject to research disturbance of band resighting efforts, adult capture, and fledgling banding. Over two field seasons, we reviewed 399,674 photographs from 32 game cameras, with 187 nests used in analyses. Nests were 16.82 times more likely to fail on days researchers visited the island compared to days they did not. Nests in 2011 were 6.16 times more likely to succeed than nests in 2010. Nests were 1.76 times more likely to succeed during the chick stage than the egg stage. Nest survival for both islands increased substantially from 2010 to 2011 averaging 50.0% and 89.1%, respectively. Nest survival over the years and islands with researcher disturbance excluded from analyses averaged 75.15% (52.3%–97.7%), compared to 69.58% (40.9%–91.8%) with researcher disturbance. Researcher disturbance had a substantial impact on cormorant nest success in 2010. When researcher visits in 2011 were limited to the chick rearing period, nest failures declined markedly on both islands, but research disturbance still had a negative effect. Our research suggests the literature on cormorant demography may underestimate nest success and survival. We recommend researchers conduct surveys after hatching and take precautions to limit disturbance, such as after dark entry and exit from colonies and use of blinds and technology (cameras, drones) where feasible and applicable.

Bird species that exhibit male-biased sexual size dimorphism (SSD) often demonstrate a female-biased fledging sex ratio (FSR). One hypothesis for this relationship is that male nestlings are more costly to raise and therefore at greater risk of mortality. However, not all male-biased size dimorphic species have been found to have a female-biased FSR, and many species have not been studied to better establish the relationship between SSD and FSR. We sought to determine the FSR of the American Robin (<em>Turdus migratorius</em>) and evaluate the relationship of SSD in the nestling stage to the FSR of the species. We also used qualitative and quantitative assessments of juvenile plumage to gauge the feasibility of sex determination through plumage. Male and female nestlings had substantial overlap in plumage characteristics, and we could not reliably distinguish between the sexes. Plumage differences between the sexes of juvenile robins may be insufficient to accurately determine sex in the field. The FSR was significantly skewed toward females; 63% of 59 nestlings were female. Size differences between male and female nestlings were minimal. Our findings do not provide strong support for the hypothesis that SSD leads to differential mortality of nestlings that skews fledging sex ratios toward the smaller sex. Other factors probably have a greater influence on the FSR of the species. More research is necessary to determine the primary drivers of skewed sex ratios in American Robins and other bird species.

Although there is abundant evidence that timing of spring migration in landbirds is influenced by annual variation in temperature and longer-term warming due to climate change, much less is known about how these factors influence fall migration, especially in North America. Similarly, less is known about the influence of annual variation in temperature and precipitation and the combination of intrinsic factors (age, sex, wintering location, diet, number of broods produced in a breeding season) on the timing of fall migration. We used 13 years of capture data, spanning a 19-year period (2006–2024) to look for species-specific evidence of multi-year change in fall migratory timing while also looking to see if precipitation amount or temperature experienced by birds using our site changed. Finally, we looked for evidence that the above extrinsic and intrinsic factors influenced annual variation in migratory timing. We found evidence that (1) 46% (6 of 13) of the species exhibited either delays (4 species) or advances (2 species) in migratory timing, (2) average temperature increased by 1.4 °C during the fall migratory period, (3) sex and wintering location influenced timing with females (2.3 days) and species that winter in Central or South America (14.3 days) passing through our site before males and species wintering in North America, and (4) in warmer and/or wetter years birds advanced timing. Our results increase understanding of how intrinsic and extrinsic factors influence annual timing of fall migration. Further, our findings add to the growing evidence that climate change has altered fall migratory timing and that differences exist in how species and populations have responded. More work is necessary to determine whether changes in timing of fall migration are due to developmental plasticity, selection on heritable variation, or some combination.

Indicator species can facilitate the assessment, management, and conservation of biodiversity. The White-headed Woodpecker (<em>Leuconotopicus albolarvatus</em>) is a species of conservation concern that is considered an indicator species for mature ponderosa pine ecosystems, a priority restoration habitat that has declined by 90% in the northern Blue Mountains, USA. Here, we employed passive acoustic monitoring at 227 randomly selected locations across two National Forests in the northern Blue Mountains. Autonomous recording units were deployed for an average of 4.41 weeks per station (SD = 1.21) and audio recordings were processed with BirdNETv2.4. White-headed Woodpecker predictions were manually reviewed to create detection/non-detection data. We estimated occupancy and detection probabilities using a Bayesian occupancy model and compared the habitat suitability between occupied and unoccupied sites. Naïve occupancy was 7.5%, and the estimated proportion of sites occupied was 0.08 (95% Credible Interval: 0.075, 0.092). The average weekly detection probability was 0.71 (0.60, 0.80), indicating we detected the species with little error when present. Following model selection, we found the odds of occupancy were 5.26 times lower for every 2.87 m²/ha increase in lodgepole pine basal area. Sites considered occupied were also found to have higher values of a habitat suitability metric currently used to inform land management decisions. Low occupancy of White-headed Woodpeckers potentially indicates the northern Blue Mountains cannot currently support a broad distribution of an indicator species for mature ponderosa pine forests. More broadly, this study provides insight into the condition of a regional, priority restoration habitat and provides important information for forest management.

Understanding the demographic characteristics of animal populations, such as age, sex, and population structure, is essential for effective wildlife management and conservation. However, accurately identifying these traits in wild populations is challenging, especially for birds inhabiting remote or sensitive wetlands. Flamingos exemplify this difficulty because their subtle sexual dimorphism makes sex identification complex. Recent advances in technology offer non-invasive methods for collecting demographic data from a distance, providing new opportunities for wildlife research. This study tested photogrammetric techniques, methods that obtain quantitative measurements from photographs, to assess sex in Chilean Flamingos (<em>Phoenicopterus chilensis</em>) by collecting key morphological data from standardized images. Captive flamingos, sexed by molecular techniques, were photographed to validate the method’s accuracy. Subsequently, the same techniques were applied to wild, free-ranging flamingos to evaluate the influence of distance, image quality, and measurement choice on identification success. Results showed that photogrammetric methods could reliably identify the sex of both wild and captive flamingos. However, accuracy depended on selecting appropriate measurements, careful application of the method, and maintaining optimal distances between the photographer and the subject. These findings highlight the potential of photogrammetry as a practical, non-invasive tool for gathering reliable demographic data. By integrating advanced technology into conservation strategies, this approach can enhance ecological studies and improve management practices for flamingos worldwide.

We examined song-type sharing and song-type co-occurrence among broadcast songs in a migratory population of a songbird with large and highly variable repertoire sizes, the Rock Wren (<em>Salpinctes obsoletus</em>). Large song-type repertoires may offer a competitive advantage in intrasexual competition and provide opportunities for varied patterns of song-type sharing. We found that Rock Wrens in one population showed a general tendency to overproduce highly shared, i.e., popular, songs, and males with smaller repertoires sang more popular songs than males with larger repertoires. Song types with lower minimum frequencies and slower trill rates tended to be more popular, potentially enhancing song transmission. Using network analyses, we found non-random song sharing between pairs of males that does not seem to be mediated by location. Song-delivery rates of males were positively related to their song sharing with other males, and it is possible that both mediate male-male aggression or female preference. We also found that some pairs of song types co-occurred in birds’ repertoires more than others, but the song co-occurrence network was not clustered, raising questions about what factors drive song co-occurrence and repertoire composition. Taken together, our results suggest that song sharing and singing locally popular songs may play an important role in social communication. The results support the notion that having a larger repertoire allows a bird to sing both rare and popular song types and use rare or unique song types that can be used in assessment by rivals, more often than birds with smaller repertoires.

Many birds are known for ornaments and behavior undertaken in the pursuit of finding and keeping a mate, but for many species, the specific factors that contribute to breeding success remain underexplored. In this study, we tracked the reproductive fates of a population of the Northern Mockingbird, <em>Mimus polyglottos</em>, on the Rice University campus in Houston, Texas. We related male mating success, total fecundity, offspring survival, and rates of extra-pair paternity to body size and condition, the timing of key reproductive events, and metrics of song and of territory quality. Our results indicate that heavier and more experienced males were significantly more likely to attract mates. Birds of both sexes that bred earlier in the season produced significantly more total offspring and enjoyed higher offspring survival. Surprisingly, although <em>M. polyglottos</em> is famous for the complexity of its song and for its high territorial aggression, we did not detect a significant effect of any metric of song or territory quality on mating success, although our song samples were short and exclusively collected early in the breeding season and other measurements might have been more successful. We also detected surprisingly few instances of extra-pair paternity or egg-dumping relative to other socially monogamous songbirds and other mockingbird studies. Our results underscore the variations in reproductive strategy that can exist between different bird species or across different environments.

The American Oystercatcher (<em>Haematopus palliatus pitanay</em>) was recently classified as Near Threatened in Chile because of concerns about low recruitment at some breeding sites. However, long-term monitoring in central Chile suggests stable populations. A potential explanation for the latter disagreement might have to do with the concept of extinction debt, the delayed population decline following habitat loss/disturbance. This delayed response complicates viability assessments, especially in species with long life spans such as the American Oystercatcher, where low recruitment may fail to offset adult mortality, thus masking impending declines. We tested this hypothesis using data from monitoring, eBird observations, and banding, with which we assessed population trends. We found annual fluctuations with predictable cycles and an overall positive trend. As expected for a long-lived species, adult survival was high (ɸa = 0.87), but reproductive success in estuary populations was low (fertility rate = 0.20). Our findings failed to find support for the extinction debt hypothesis, but suggest that some estuaries may act as population sinks in a regional source-sink system. However, more data are needed to confirm this mechanism. Understanding these dynamics is crucial for proactive conservation efforts to prevent delayed declines and ensure the persistence of this species.