Approximately 97% of all bird species are considered diurnal, although diel activity patterns of birds may be more flexible than previously believed. Much remains unknown about nocturnal activity in typically diurnal birds, which may result in potential loss of information about an important aspect of their behavior and ecology. Parrots (Order Psittaciformes), except for the truly nocturnal species, are generally not known to be active at night. However, Kākā ( Nestor meridionalis ) is an interesting candidate to understand how nocturnal investigations can challenge the preconceptions of avian activity patterns. Kākā are large forest parrots endemic to Aotearoa New Zealand, with historical and anecdotal evidence of remaining active after dark. We conducted the first field study to assess the activity of wild Kākā during both night and day, using ad libitum and instantaneous sampling techniques. In 122 sampling hours, we recorded 326 Kākā encounters, 17.5% of which occurred at night. In addition to resting, Kākā were observed moving through and flying above the canopy, grooming, and foraging nocturnally. The estimated percentages of observed behaviors differed between sampling techniques, as higher estimates of relatively inconspicuous behaviors, such as resting, were detected using instantaneous sampling. Kākā vocalized during day and night, with high-pitched, long-distance calls being predominant at both times of day. Nocturnal call rates were unrelated to moon phases. Our findings suggest that Kākā exhibit partial nocturnality, which is an unexplored aspect of parrot ecology with implications for conservation and habitat management. Paying greater attention to nocturnal behaviors in typically diurnal species may offer valuable insights for conservation in response to artificial light at night and noise pollution in a rapidly urbanizing environment.
The Cuban Gnatcatcher (Polioptila lembeyei) is an endemic bird with a discontinuous distribution in Cuban coastal scrublands and its effective conservation requires a fine-scale understanding of its distribution. Although lacking an IUCN threat category, it faces critical pressures from habitat fragmentation and climate change. This study characterizes its spatiotemporal distribution and habitat associations in the eastern sector of the Siboney-Jutici Ecological Reserve using data from 2012-2014 and 2016. Through variable-radius point counts and playback surveys, geostatistical analyses revealed a significantly clustered distribution pattern. Core areas of secure presence and high detection density were concentrated in the south of the study area, while absence zones predominated in the north. The species showed strong restriction to coastal and precoastal xeromorphic scrub but exhibited heterogeneous distribution within this habitat. Temporal analysis demonstrated interannual stability in core distribution areas and no significant detection rate differences between breeding and non-breeding seasons. Verification surveys confirmed persistent absence zones not attributable to detectability issues. Vegetation analysis showed that presence areas had significantly lower canopy cover and tree density, confirmed by a negative binomial GLM identifying tree abundance as a significant negative predictor. Complementary analysis revealed significantly lower normalized difference vegetation index (NDVI) values in presence areas, reinforcing the species' preference for open, low-stature vegetation. These findings demonstrate high microhabitat specificity within the scrub matrix. This provides crucial insights for refining national distribution models through appropriate variable selection, particularly vegetation structure and NDVI. Furthermore, these insights guide targeted conservation strategies for this endemic species by identifying and protecting essential habitat patches that support its core populations.
Drone surveys provide accurate estimates of nest abundance and survival for ground-nesting waterbird species, but drones have not been used to estimate survival for waterbirds nesting in a canopied swamp habitat. We compared nest survival of Snowy Egret ( Egretta thula ), Great Egret ( Ardea alba ), Tricolored Heron ( Egretta tricolor ), Glossy Ibis ( Plegadis falcinellus ), and Cattle Egret ( Ardea ibis ) between traditional ground surveys and drone survey methods in freshwater wetland habitats of Florida, USA, in 2021. Overall, there were minimal differences in survival estimates between methods. However, drone-derived estimates of dark-colored waterbirds had lower accuracy than drone-derived estimates of white-colored waterbirds. Our results suggest that drone surveys provide comparable estimates to traditional ground-based methods for nest survival of waterbirds breeding in swamp habitat, and they offer the advantage of causing less disturbance to birds than traditional methods if flown at appropriate altitudes and following best practices.
The Blood Pheasant ( Ithaginis cruentus ) may be unique amongst Galliformes species in that it is believed to forage primarily on bryophytes. Yet there are few quantitative studies that have examined the species diet and how this might vary seasonally, as these data could shed some light on how such species are able to adapt to harsher, cold montane environments. To help fill this knowledge gap, we used microhistological fecal analysis to determine the dietary composition of a Blood Pheasant population at Lianhuashan Nature Reserve in Gansu Province, China. A total of 149 fresh feces samples of Blood Pheasant were collected continuously from April 2011 to October 2013 (spanning all four seasons) along 18 km of roads in the reserve. Bryophytes were the most abundant items in the fecal samples (99.8%), of which 11 families were recognized. Mniaceae was present in nearly all fecal samples and constituted the main dietary component across the population. There was significant seasonal variation in bryophyte presence in fecal samples, with the proportion of bryophytes lowest in summer, and highest during autumn. In addition, the digestibility of bryophytes was also highest in autumn compared to other seasons. Our results highlight a degree of dietary plasticity by Blood Pheasants and we discuss how this variation enables them to adapt to local seasonal climatic conditions in their montane environment.
Molt is the periodic replacement of a bird's plumage within the annual cycle. Replacements outside the known annual molt strategy of each species are considered accidental. During the winter of 2023-2024 in Barcelona city, we found evidence of a second plumage replacement in birds of three passerine species with only one known molt in their annual cycle: House Sparrow and Blue and Great tits. To evaluate how this fits our understanding of molt, we first considered whether these feathers could result from a delayed molt or from a new replacement occurring after the species' scheduled molt. We ruled out the possibility of a delayed scheduled molt because the plumage was in fresh condition. We therefore examined whether these replacements could be treated as molt or as accidental feather replacement. To do so, we quantified two components of the molt process (intensity and sequence) and two components of the molt output (extent and asymmetry). Values of the four molt components were lowest in the House Sparrow, intermediate for the Blue Tit, and highest in the Great Tit. Using values of molt components, we propose three rules to determine whether unscheduled plumage replacements should be regarded as an actual extra molt episode or just accidental plumage replacement. From these rules, we concluded that the House Sparrow exhibited an accidental replacement or a highly asymmetrical extra molt episode, whereas both tit species were undergoing an extra molt episode, though asymmetrical in the Blue Tit. Unscheduled plumage replacement may not be an adaptive trait in some species, but could facilitate the evolution of more complex molt strategies and new plumage functions in other species.
Trends in wildlife mortality can be particularly challenging to identify in low-density species where mortalities are less likely to be detected or documented. The Pueo, or Hawaiian Short-eared Owl ( (Asio flammeus sandwichensis), is the only native raptor that breeds on all the main Hawaiian Islands. The Pueo is state-listed as endangered on the island of O'ahu, but drivers of population dynamics are not well known, including causes of mortality. In this study, existing records from organizations across the Hawaiian Islands were compiled to evaluate the causes of mortality in Pueo. Here, 242 unique records spanning the years 1993 to 2024 from state, federal, and private organizations were evaluated for causes of Pueo death. Trauma due to collisions with vehicles, wind turbines, fences, and other human-made objects was the leading detected cause of death (62%) followed by emaciation (13%) and disease (6%), with 19% of deaths due to unknown causes. The islands of Hawai'i and Kaua'i, both with relatively low human populations, had the highest total number of reported mortalities (n = 77, 32%). The highest number of recorded mortalities was in the month of July (16%), and mortalities were generally higher from June through August. Although our study has detection biases, our results are consistent with global studies suggesting that blunt force trauma from vehicles, wind turbines, and other infrastructure are potentially important sources of mortality in raptors. Similar to other studies, rodenticide effects and infectious disease were potentially underestimated as sources of mortality, because most birds did not undergo a full necropsy. Further, there may be confounding variables due to ad hoc data collection. Development of a state-wide system for reporting and recording wildlife mortality along with future studies that include necropsies may improve our ability to discern which sources of mortality may be mitigated.
Blood parasites can influence avian physiology, behavior, and reproduction, yet their prevalence and diversity vary across hosts, environments, and latitudes. We assessed haemosporidian infections in the migrant Chilean Swallow ( Tachycineta leucopyga ) at two widely separated breeding populations in Argentine Patagonia. Molecular screening of the parasite mitochondrial cytochrome b gene conducted on 209 individuals revealed a single Leucocytozoon -infected adult in Tierra del Fuego; no other infections were detected. Blast and phylogenetic analyses identified the parasite as belonging to the lineage DIUDIU11. This lineage has been previously reported in several South American passerine species and is closely related to Leucocytozoon fringillinarum . Our results revealed extremely low hemoparasite prevalence in this aerial insectivore, likely reflecting limited vector contact because of their behavior, low vector abundance, or the absence of infectious parasites at breeding and/or non-breeding sites. These findings establish a first baseline for hemoparasite dynamics in a long-term monitored South American swallow population and emphasize the importance of assessing migratory birds’ health across their full annual cycle under ongoing environmental change and climate warming.
Approximately 97% of all bird species are considered diurnal, although diel activity patterns of birds may be more flexible than previously believed. Much remains unknown about nocturnal activity in typically diurnal birds, which may result in potential loss of information about an important aspect of their behavior and ecology. Parrots (Order Psittaciformes), except for the truly nocturnal species, are generally not known to be active at night. However, K & amacr;k & amacr; (Nestor meridionalis) is an interesting candidate to understand how nocturnal investigations can challenge the preconceptions of avian activity patterns. K & amacr;k & amacr; are large forest parrots endemic to Aotearoa New Zealand, with historical and anecdotal evidence of remaining active after dark. We conducted the first field study to assess the activity of wild K & amacr;k & amacr; during both night and day, using ad libitum and instantaneous sampling techniques. In 122 sampling hours, we recorded 326 K & amacr;k & amacr; encounters, 17.5% of which occurred at night. In addition to resting, K & amacr;k & amacr; were observed moving through and flying above the canopy, grooming, and foraging nocturnally. The estimated percentages of observed behaviors differed between sampling techniques, as higher estimates of relatively inconspicuous behaviors, such as resting, were detected using instantaneous sampling. K & amacr;k & amacr; vocalized during day and night, with high-pitched, long-distance calls being predominant at both times of day. Nocturnal call rates were unrelated to moon phases. Our findings suggest that K & amacr;k & amacr; exhibit partial nocturnality, which is an unexplored aspect of parrot ecology with implications for conservation and habitat management. Paying greater attention to nocturnal behaviors in typically diurnal species may offer valuable insights for conservation in response to artificial light at night and noise pollution in a rapidly urbanizing environment.
Many migratory birds show breeding-site fidelity, but research has focused primarily on shrubland and forest species, with grassland birds largely overlooked. Fidelity is typically higher in woody systems because of the greater predictability and stability of these environments. Furthermore, breeding-site fidelity has been shown to influence territory size, with returning birds occupying higher-quality habitat in familiar landscapes and maintaining smaller territories. We investigated Western Meadowlark (Sturnella neglecta) breeding-site fidelity in the Northern Great Plains from 2022 to 2024, with objectives to (1) quantify breeding-site fidelity in grasslands managed with fire and grazing, and (2) characterize the relationship between individual breeding-site fidelity and territory size. We observed high breeding-site fidelity, with annual return rates of 61% in 2023 and 60% in 2024, and 33% of birds banded in 2022 returning in both subsequent years. Territory sizes declined over time regardless of return status (2022: mean = 7.80 ha; 2024: mean = 5.50 ha; chi 22 = 7.86, p = 0.02). Mean territory size did not differ by return status (chi 22 = 0.53, p = 0.77) and variability in territory size was not different between returning and non-returning birds (F1,68 = 3.39, p = 0.07). We documented strong breeding-site fidelity in Western Meadowlarks. Although the drivers of this fidelity remain uncertain, several non-exclusive mechanisms may contribute, including stable habitat maintained through fire and grazing, individual experience, and landscape configuration that limits dispersal. Declines in meadowlark territory size over time may reflect interannual variation in precipitation. Precipitation likely influences resource availability, with wetter years allowing birds to establish smaller, more resource-rich territories. Our findings contribute additional evidence that grassland birds can exhibit strong breeding-site fidelity despite dynamic management and environmental conditions and highlight the need for future research explicitly linking management regimes, environmental variability, and individual behavior.
Artificial nest boxes are an important tool for studying the breeding biology of birds. Additionally, they can provide valuable nest sites for secondary cavity-nesting birds when they are limited, but despite these potential benefits, if poorly constructed or placed, artificial cavities may act as ecological traps. The Prothonotary Warbler (Protonotaria citrea) is awetland-dependent secondary cavity-nesting bird that prefers to nest over water and as a consequence, its nests are vulnerable to flooding. The Prothonotary Warbler has declined by 38% in the past 50 years and floods are becoming more frequent with the changing climate making this species more susceptible to nest loss from flooding. Nest boxes mounted at heights of 1.5 m to maximize ease of sampling by researchers are prone to inundation even in moderate flood conditions. Here, we describe a novel design for a flood-resistant nest box that provides both convenient access for researchers and a safe location for Prothonotary Warblers above most flood waters. Our nest box is made of polyvinyl chloride ("PVC") and is attached to a 3 m electrical conduit pole. The box is attached to the pole allowing it to be elevated with paracord safely above flood waters and then lowered to the check nest contents. We began using these nests boxes in 2018 and they remained above flood waters in 2018 and 2023, but they were submerged during the historic flood of the Mississippi River in 2019, which crested at a record high level. Our flood-resistant nest box is ideal for researchers studying the breeding biology of secondary cavity-nesting birds that nest near water.
Despite its ecological importance as a predatory passerine, the Northern Shrike (Lanius borealis) remains severely understudied. In North America, this species breeds in the boreal taiga and taiga-tundra ecotone and winters across much of the northern continental United States and southern Canada. Because of its remote breeding range, population estimation for this species is challenging, and little is known about its population structure, movement, or habitat use. However, wintering populations in Minnesota provide a unique opportunity to study Northern Shrikes' non-breeding ecology, as the birds are more accessible, and their habitat preferences are easier to observe during this time. To fill these gaps in knowledge, we (1) analyzed morphometric and demographic data on Northern Shrikes (n = 58) banded in northeastern Minnesota between 2021 and 2024, (2) deployed light-level geolocators (n = 31) on non-breeding Northern Shrikes between 2021 and 2022, and (3) identified land cover preferences throughout Minnesota based on 1185 Northern Shrike eBird observations. We found a significantly higher number of adults present during the winter. Adult males averaged significantly larger than adult females by wing chord and tail length, and adults were significantly longer winged than juveniles. A combination of poor non-breeding site fidelity and near-zero recapture rates prevented the recovery of any geolocator units. Using resource selection functions, we identified that Northern Shrikes used grassland, water, wetland, and developed land in greater proportion to what was available on the landscape, but selected against cropland and forest. Northern Shrikes also preferentially selected for areas with a greater number of land cover types present, indicating a potential preference for heterogeneous landscapes. Our results provide the first description of Northern Shrike demographics, tracking technology deployment, and large-scale non-breeding habitat associations for this species in Minnesota. RESUMEN. A pesar de su importancia ecol & oacute;gica como paseriforme depredador, Lanius borealis sigue siendo una especie escasamente estudiada. En Am & eacute;rica del Norte, esta especie se reproduce en la taiga boreal y en el ecotono taiga-tundra, y pasa el invierno en gran parte del norte de Estados Unidos continental y del sur de Canad & aacute;. Debido a su remota & aacute;rea de reproducci & oacute;n, la estimaci & oacute;n de la poblaci & oacute;n de esta especie resulta dificil, y se conoce poco sobre su estructura poblacional, movimientos o uso del h & aacute;bitat. Sin embargo, las poblaciones invernantes en Minnesota ofrecen una oportunidad singular para estudiar la ecologia no reproductiva de L. borealis, ya que los individuos son m & aacute;s accesibles y sus preferencias de h & aacute;bitat son m & aacute;s f & aacute;ciles de observar durante este periodo. Para llenar estos vacios de conocimiento, (1) analizamos datos morfom & eacute;tricos y demogr & aacute;ficos de L. borealis (n = 58) anillados en el noreste de Minnesota entre 2021 y 2024, (2) colocamos geolocalizadores basados en niveles de luz (n = 31) en individuos no reproductivos entre 2021 y 2022, y (3) identificamos las preferencias de cobertura del suelo en todo Minnesota a partir de 1185 observaciones de eBird de la especie. Encontramos un n & uacute;mero significativamente mayor de adultos presentes durante el invierno. Los machos adultos fueron, en promedio, significativamente m & aacute;s grandes que las hembras adultas en cuanto a la cuerda alar y la longitud de la cola, y los adultos mostraron alas significativamente m & aacute;s largas que los juveniles. Una combinaci & oacute;n de baja fidelidad al sitio durante el periodo no reproductivo y tasas de recaptura cercanas a cero impidi & oacute; la recuperaci & oacute;n de alg & uacute;n geolocalizador. Mediante funciones de selecci & oacute;n de recursos, identificamos que L. borealis utiliz & oacute; pastizales, cuerpos de agua, humedales y & aacute;reas desarrolladas en una proporci & oacute;n mayor que la disponible en el paisaje, pero seleccion & oacute; negativamente cultivos y bosques. L. borealis tambi & eacute;n seleccion & oacute; preferentemente & aacute;reas con un mayor n & uacute;mero de tipos de cobertura de suelo, lo que indica una posible preferencia por paisajes heterog & eacute;neos. Nuestros resultados proporcionan la primera descripci & oacute;n de la demografia, implementaci & oacute;n de tecnologia de seguimiento y asociaciones de h & aacute;bitat a gran escala durante el periodo no reproductivo de esta especie en Minnesota.
. Acoustic communication is essential for exchanging information between individuals of the same species. In birds, song plays a vital role in mate attraction and territory defense, and when it varies between populations, it can create barriers to gene flow and promote speciation. The Belding's Yellowthroat (Geothlypis beldingi) is an endemic bird of the Mexican state of Baja California Sur and is endangered because of declining populations. Its populations are small and highly fragmented, but knowledge of the effects of fragmentation on the ecology and behavior of this species, especially its songs, remains limited. Five allopatric populations along its distribution were studied to assess their acoustic geographic variation. Six acoustic variables from 31 individual songs were analyzed using two supervised classification and multivariate techniques. Our results revealed significant differences between the northern and southern populations, which are separated by approximately 350 km, but the relationship between geographic distance and song variation is limited and could be influenced by different factors. Our results suggest that population-level acoustic differentiation may be associated with the "archipelago-like" distribution of oases. This association with fragmentation should be corroborated by more phenotypic characters and genetic information to determine if there are two significant evolutionary units within this species or lineages at the species level.
California's Sacramento Valley has lost much of its native riparian and wetland habitats because of anthropogenic land-use change. Efforts to restore habitat have occurred, and bird responses have been primarily studied on public lands, whereas restoration on private lands remains largely understudied. We assessed avian occupancy using passive acoustic monitoring during the breeding season on a private hunting club, comprising a heterogenous mix of rice, managed wetlands, and native riparian forest, in the Central Valley's Butte Basin, California, USA. In total, we detected 85 bird species. We detected 95% of the known breeding passerines on the property. Using a multi-species occupancy model, we determined occupancy by habitat for 21 of the most common species on the property, which revealed riparian and oak habitat specialists and reflects occupancy patterns documented for other regions in the Central Valley. We found that native riparian strips support greater species richness compared to marsh and rice habitats, with an average of 30 (90% CI: 2-32) passerine species and 13 (90% CI: 11-16) non-passerine species, despite representing 7% of total land cover. These findings can be used to encourage restoration and protection of native riparian habitat as a practice adopted by private landowners interested in maintaining overall avian diversity on their lands. Passive acoustic monitoring proved an effective method to characterize the overall avian community on this 1020 ha property. However, we believe that there is a lower limit of parcel size to allow for enough independent samples and data to be used in occupancy models. Based off our results, using audio recording units at the parcel level yield species diversity results for breeding passerines comparable to traditional avian survey methods and would provide a less invasive, long-term monitoring technique on private properties, particularly for passerines. RESUMEN. El Valle de Sacramento de California ha perdido gran parte de sus h & aacute;bitats ribere & ntilde;os y de humedales nativos debido a cambios de uso de la tierra antropog & eacute;nicos. Han ocurrido esfuerzos para restaurar h & aacute;bitats, y las respuestas de aves han sido primariamente estudiadas en tierras p & uacute;blicas, sin embargo, la restauraci & oacute;n en tierras privadas sigue poco estudiada. Hemos evaluado la ocupaci & oacute;n de aves usando monitoreo ac & uacute;stico pasivo durante la & eacute;poca reproductiva en un club de caza privado, que comprende una mezcla heterog & eacute;nea de arrozales, humedales manejados y bosque ribere & ntilde;o nativo, en la Cuenca del Valle Central de Butte, California, USA. En total, detectamos 85 especies de aves. Detectamos 95% de los paseriformes en reproducci & oacute;n conocidos en la propiedad. Usando un modelo de ocupaci & oacute;n multi-especies, hemos determinado la ocupaci & oacute;n de h & aacute;bitat para 21 de las especies m & aacute;s comunes en la propiedad, lo cual revel & oacute; aves especialistas de h & aacute;bitats ribere & ntilde;os y h & aacute;bitats de robles, y esto refleja patrones de ocupaci & oacute;n documentados para otras regiones en el Valle Central. Hemos encontrado que las franjas ribere & ntilde;as nativas albergan una mayor riqueza de especies en comparaci & oacute;n con h & aacute;bitats de marismas y arrozales, con un promedio de 30 (90% CI: 2-32) especies de paseriformes y 13 (90% CI: 11-16) de especies no-paseriformes, aunque representen 7% del total de cobertura de la tierra. Estos hallazgos pueden utilizarse para fomentar la restauraci & oacute;n y protecci & oacute;n del h & aacute;bitat ribere & ntilde;o nativo como pr & aacute;ctica adoptada por propietarios privados interesados en mantener la diversidad general de aves en sus tierras. El monitoreo ac & uacute;stico pasivo demostr & oacute; ser un m & eacute;todo efectivo para caracterizar la comunidad de aves general en esta propiedad de 1020 hect & aacute;reas. Sin embargo, creemos que existe un l & iacute;mite menor en el tama & ntilde;o de parcela para permitir muestras independientes y datos suficientes para ser usados en modelos de ocupaci & oacute;n. En base a nuestros resultados, el uso de unidades de grabaci & oacute;n de audio a nivel de parcela produce resultados de diversidad de paseriformes en reproducci & oacute;n comparables con m & eacute;todos tradicionales de censo de aves y podr & iacute;a proporcionar una t & eacute;cnica de monitoreo menos invasiva y de largo plazo en propiedades privadas.
Prior to migration, songbirds increase food consumption to deposit subcutaneous fat that helps fuel migratory flights, and many periodically pause at stopover sites to rest and refuel for the next flight. We conducted a three-phase, proof-of-concept study to move toward a standardized approach to collecting and preparing fat samples from wild, migrating songbirds, and to explore the feasibility of using stable-isotope analysis on fat tissue to estimate previous stopover locations. First, using fat obtained from a storebought chicken breast, we conducted an experiment to test whether lipid purification method affects percent lipid yield and stable hydrogen (b2H) and stable carbon (b13C) isotope values. We found that purified lipids had significantly higher b2H values and lower b13C values than whole fat samples indicating the need for consistency in sample preparation. Second, to test for repeatability in b2H and b13C values in purified lipids obtained from wild songbirds, we held Swainson's Thrushes (Catharus ustulatus; n = 9) in temporary captivity provided with the same diet and local water, and found remarkable consistency in both b2H (SD = 2.6%o) and b13C (SD = 0.3%o) values between individuals. Third, we sampled fat from seven species (Magnolia Warbler [Setophaga magnolia], Swainson's Thrush, Hermit Thrush [Catharus guttatus], Wood Thrush [Hylocichla mustelina], Gray Catbird [Dumetella carolinensis], Red-eyed Vireo [Vireo olivaceus], Northern Waterthrush [Parkesia noveboracensis]) of wild, migrating songbirds at Powdermill Nature Reserve, Pennsylvania, USA as a preliminary investigation into the usefulness of stable-isotope analysis in estimating geographic location of fat assimilation. Among five species assumed to have deposited fat at distant latitudes during spring migration, the three thrush species had b2H values consistent with latitudes farther south relative to Magnolia Warblers and Gray Catbirds. However, in the two species (Red-eyed Vireo and Northern Waterthrush) assumed to have assimilated fat locally, there was significant variation in b2H values between the species, and b2H values did not fit into the pattern observed in distant-origin birds. Although geographic assignment of fat assimilation site in migrating songbirds is more complicated than we expected, stable-isotope analysis of fat is a promising method with potential applications in stopover ecology, diet, and habitat use.
. The Least Flycatcher (Empidonax minimus), a small migratory songbird, has experienced significant population declines across its North American range over the past five decades. Whereas the causes of this decline remain complex and multifaceted, habitat loss, fragmentation, and changes in forest composition on the breeding grounds are suspected to play a critical role. To better understand the relationship between breeding habitat and reproductive success, we estimated nesting success across a gradient of increasing forest cover, i.e., 46% to 85%, at seven sites in Minnesota. Data from 171 nests revealed substantial variation in nesting success, ranging from 37% at the site with the lowest forest cover to 94% at the most forested site. Nesting success was significantly higher in landscapes dominated by northern hardwood forests, particularly those with abundant sugar maple (Acer saccharum), and in nests located lower in the canopy. These findings suggest that forest composition and landscape-scale forest cover are important predictors of reproductive success in Least Flycatchers. Although limited to a single breeding season, this study contributes to our understanding of the species' breeding ecology and the importance of extensive northern hardwood forest, especially of mixed-age sugar maple and paper birch (Betula papyrifera), at both local, i.e., 100-m, and landscape, i.e., 10-km, scales. reproducci & oacute;n y el & eacute;xito reproductivo, estimamos el & eacute;xito de nidificaci & oacute;n a lo largo de un gradiente de cobertura forestal creciente, i.e., forestal a escala de paisaje son importantes predictores del & eacute;xito reproductivo del Mosquero Minimo. Aunque limitado a una sola de distintas edades, tanto a escala local, i.e., 100 m, como a escala de paisaje, i.e., 10 km.
The most frequently reported negative effect of human disturbance in gull colonies is an increase in chick mortality. This is primarily caused by the presence of humans startling nearby chicks, prompting them to flee out of their own territories where they are attacked by adults of adjacent territories. This effect may be exacerbated in handled chicks. This study proposed and evaluated a simple, non-invasive procedure designed to keep older Yellow-legged Gull (Larus michahellis) chicks within their territories after handling and release. The procedure consisted of placing the chicks on the ground in a supine position, with their heads positioned behind their bodies in a way that deprived them of vision. This procedure (vision-deprived supine release) is only appropriate for chicks that are at least three weeks old. Results demonstrated that the procedure significantly increased the time chicks remained at the release site. Moreover, more than half of the sampled chicks did not regain their natural standing posture until enough time had passed for the researcher to have retreated to a distance of approximately 150 m or more, a distance considered sufficient to minimize human disturbance. The only potentially negative aspect of this procedure was that a very small proportion of chicks (n = 1) were not able to roll over and regain their natural standing posture. Although it was uncommon, it should be further investigated. Overall, the visiondeprived supine release may substantially contribute to minimizing investigator-induced disturbance during chick handling in gull colonies.
There is limited information on migratory ecology, nonbreeding grounds, and return rates from populations at distributional limits of species' ranges. Assuming uniform ecology from core areas to range periphery may limit understanding of potential migratory routes, nonbreeding distribution, and connectivity, complicating conservation actions and assessing species-level management. We tracked a relatively well-studied Nearctic-Neotropical migratory wood-warbler, the Ovenbird (Seiurus aurocapilla), breeding in atypical habitats at their distributional limit in northwestern Nebraska. Individuals wintered in northwestern Mexico and migrated through the southwestern U.S., western and central Great Plains. Compared to previous studies of birds breeding in core range, the migration routes and nonbreeding areas used by western Nebraska Ovenbirds also represent the seasonal distributional limits for this species. Despite a small sample size, male return rates were also relatively high and comparable to populations breeding in large, contiguous forest regions of the core range. Overall, this study adds novel data from range periphery for a well-studied species, further reinforcing the importance of full annual cycle data and studying birds across all parts of their distribution.
. 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, Mimus polyglottos, 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 M. polyglottos 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.
