Competition for nesting sites among secondary cavity nesters, which rely on existing cavities produced by other species or artificial nest boxes, is fierce. Tits (Paridae) are known to occupy and lay eggs in the nests of other species. Here, we report five cases of nest usurpation related to Asian Tits (Parus cinereus minor) in three provinces of China: (1) Willow Tits (Poecile montanus) usurping an Asian Tit nest, (2) Asian Tits usurping the nest of an Oriental Magpie-Robin (Copsychus saularis), (3) Asian Tits usurping the nest of a Willow Tit, (4) Asian Tits usurping a nest of a Coal Tit (Periparus ater), and (5) Coal Tits usurping an Asian Tit nest. In four of the five cases, mixed broods were successfully fledged. Our results add to the documented cases of successful mixed broods in nest usurpation events associated with this family.
New World sparrows (Passerellidae) are often secretive, and observations of behavior at their nest sites are limited. We documented courtship feeding during incubation (incubation feeding) in a secretive, endangered subspecies, the Florida Grasshopper Sparrow (Ammodramus savannarum floridanus). Successful incubation feeding occurs in a breeding pair of sparrows when the male brings food items to the nest site and passes food directly to the female, who is actively incubating eggs. We reviewed 740 h of nest camera footage across 26 breeding pairs of Florida Grasshopper Sparrows from 2022 -2024 at Three Lakes Wildlife Management Area (Osceola County, Florida, USA). We observed incubation feeding attempts at 20 of 29 nests (55 total attempts, 40 of which were successful), suggesting that male provisioning of incubating females is present, though infrequent, in this population. Most unsuccessful feeding attempts were due to female absence from the nest site (n =12). The low rates of incubation feeding suggest that females do not rely on males for supplying nutrition during incubation; rather, incubation feeding likely reinforces pair bonds. Our observations of incubation feeding behaviors for this endangered subspecies provide a baseline for future studies on how social interactions influence other reproductive behaviors and fitness. Las aves de la familia Passerellidae suelen ser sigilosos y las observaciones del comportamiento en sus nidos son limitadas. Documentamos la alimentaci & oacute;n de cortejo durante la incubaci & oacute;n (alimentaci & oacute;n de incubaci & oacute;n) en una subespecie sigilosa y en peligro de extinci & oacute;n, Ammodramus savannarum floridanus. La alimentaci & oacute;n durante la incubaci & oacute;n se produce con & eacute;xito en una pareja reproductora cuando el macho lleva alimentos al lugar del nido y se los pasa directamente a la hembra, que est & aacute; incubando los huevos. Revisamos 740 h de grabaciones de video en nidos de 26 parejas reproductoras de Ammodramus savannarum floridanus entre 2022-2024 en Three Lakes Wildlife Management Area (condado de Osceola, Florida, EE.UU.). Observamos intentos de alimentaci & oacute;n durante la incubaci & oacute;n en 20 de 29 nidos (55 intentos en total, 40 de los cuales tuvieron & eacute;xito), lo que sugiere que el aprovisionamiento de las hembras durante la incubaci & oacute;n, por parte de los machos, est & aacute; presente, aunque es infrecuente, en esta poblaci & oacute;n. La mayor & iacute;a de los intentos de alimentaci & oacute;n infructuosos se debieron a la ausencia de la hembra del lugar del nido (n = 12). Las bajas tasas de alimentaci & oacute;n durante la incubaci & oacute;n sugieren que las hembras no dependen de los machos para alimentarse durante la incubaci & oacute;n; m & aacute;s bien, la alimentaci & oacute;n durante la incubaci & oacute;n probablemente refuerza los v & iacute;nculos de pareja. Nuestras observaciones de los comportamientos de alimentaci & oacute;n durante la incubaci & oacute;n en esta subespecie en peligro de extinci & oacute;n proporcionan una base para futuros estudios sobre c & oacute;mo las interacciones sociales influyen en otros comportamientos reproductivos y en el fitness.
Abandoned nests of social wasps are sometimes occupied by animals, especially insects and arachnids, but there are few reports of their occupation by birds. We report nest excavation and successful reproduction by Yellow-chevroned Parakeets (Brotogeris chiriri) in an abandoned nest of the social wasp Polybia scutellaris (Vespidae: Polistinae). The record occurred by chance on a rural property associated with forest fragments in the northern region of the state of S & atilde;o Paulo, southeastern Brazil. The parakeets' use of a wasp nest might have been stimulated by a scarcity of nesting sites, but wasp nests could also confer benefits in terms of thermoregulation and predator deterrence. Further studies may indicate the frequency with which birds use social wasp colonies for nesting and the factors that motivate and regulate this interaction. Ninhos abandonados de vespas sociais s & atilde;o utilizados por diferentes animais, como insetos e aracn & iacute;deos; no entanto, h & agrave; poucos dados sobre sua ocupa & ccedil;& atilde;o por aves. Relatamos o comportamento de escava & ccedil;& atilde;o e a reprodu & ccedil;& atilde;o bem-sucedida do periquito-de-encontro amarelo (Brotogeris chiriri) em um ninho abandonado da vespa social Polybia scutellaris (White, 1841). O registro ocorreu por acaso em uma propriedade rural associada a fragmentos florestais na regi & atilde;o norte do estado de S & atilde;o Paulo, sudeste do Brasil. O uso do ninho da vespa pelos periquitos pode ter sido estimulado pela escassez de locais para nidifica & ccedil;& atilde;o, embora os ninhos de vespas sociais tamb & eacute;m possam conferir benef & iacute;cios relacionados & agrave; termorregula & ccedil;& atilde;o e & agrave; defesa contra predadores. Estudos futuros poder & atilde;o indicar a frequ & ecirc;ncia com que as aves utilizam col & ocirc;nias de vespas sociais para nidifica & ccedil;& atilde;o, bem como os fatores que motivam e regulam essa intera & ccedil;& atilde;o.
I documented an adult Fasciated Wren (Campylorhynchus fasciatus) feeding a juvenile Striped Cuckoo (Tapera naevia) in an inter-Andean seasonally dry forest of Peru. Although nest parasitism was not directly confirmed, this record suggests a possible host-parasite interaction and adds the genus Campylorhynchus among the potential hosts of T. naevia. C. fasciatus are cooperative breeders with communal nesting, adding to the evidence that T. naevia can parasitize birds with a cooperative breeding system, a phenomenon rarely documented among Neotropical cuckoos. Se documenta un adulto de cucarachero ondeado (Campylorhynchus fasciatus) alimentando a un juvenil de cuclillo listado (Tapera naevia) en un bosque seco interandino de Per & uacute;. Si bien no se confirm & oacute; directamente el parasitismo en un nido, este registro sugiere una posible interacci & oacute;n hospedero-par & aacute;sito y agrega al g & eacute;nero Campylorhynchus entre los hospederos potenciales de T. naevia. C. fasciatus tienen un sistema reproductivo de cr & iacute;a cooperativa y anidaci & oacute;n comunitaria, lo que suma a la evidencia de que T. naevia puede parasitar a aves con sistema de reproducci & oacute;n cooperativa, un fen & oacute;meno escasamente documentado en cucos neotropicales.
Several factors may explain patterns of conspecific aggression in breeding birds including mating systems, access to resources such as nest sites and risk of brood parasitism. In most species, the potential for social polygamy and/or extra-pair fertilizations leads to a common pattern in which intrasexual aggression is greater than intersexual aggression. I studied reactions to conspecifics in Northern Flickers (Colaptes auratus), a woodpecker with an unusual mating system of facultative polyandry and with no extra-pair fertilization. Experimental presentations of taxidermic models of both sexes to 26 male and 24 female flickers at their nesting cavity during the egg-laying stage showed that males physically attacked females with equal intensity as they did males. In females, intrasexual aggression was higher than intersexual aggression because females often assumed defensive behavior toward model males rather than attacking them. A high level of aggression to intruding females by both sexes is best explained by the risk of brood parasitism. Unlike the case in many species of birds, intrasexual aggression in male Northern Flickers is not linked to the loss of paternity or of a territory but seems to be driven by the risk of losing a nest cavity, a limited resource.
We document the effect of an extreme weather event during 21-22 June 2025 on nesting Gray Flycatchers (Empidonax wrightii) at 1,780-1,845 m elevation in sagebrush habitat of Beaverhead County, southwestern Montana, USA. The storm, cold light rain of similar to 24 h duration with occasional wet snow, was accompanied by low clouds, gusty winds, and ambient temperatures near or below freezing at night and early morning. Eleven of 16 flycatcher nests active at the beginning of the storm contained newly hatched nestlings; the remaining five contained eggs. Ten of 11 nests with nestlings failed by 23 June, one nest still in the egg-laying phase also failed. Females associated with each failed nest built replacement nests in original territories 13-95 m (mean = 42 m) from earlier nests in similar locations within the sagebrush cover, and initiated replacement clutches in 7-10 days. Clutch size in replacement nests (n = 10) was smaller (mean = 2.9 eggs) than in failed nests (mean = 3.9 eggs). All five nests that survived the storm produced fledglings (mean = 2.8), as did 7 of 11 replacement nests (mean = 2.7), although all 11 replacement nests combined produced fewer fledglings (mean = 1.7). This natural perturbation resulted in what potentially are significant reproductive costs for the flycatchers, including (1) reduced time for most pairs to attempt second broods following renesting, regardless of replacement-nest fate; and (2) lowered reproductive potential of replacement nests that were attempted. Timing of the storm relative to stage of nesting was critical. We documented only one case of double brooding in 2025, in which a pair that was brooding newly hatched young during the storm event laid a second clutch (three eggs) after two young from the first nest fledged; the second nest failed to produce fledglings. Documentamos el efecto de un evento meteorol & oacute;gico extremo durante el 21-22 de junio de 2025 en mosqueros Empidonax wrightii que anidaban a una elevaci & oacute;n de 1,780-1,845 m en matorral de Artemisia en Beaverhead County al suroeste de Montana, EUA. La tormenta, lluvia ligera fr & iacute;a con una duraci & oacute;n similar to 24 h con aguanieve ocasional, ven & iacute;a acompa & ntilde;ada de nubes bajas, r & aacute;fagas de viento y temperaturas ambientales cerca o debajo del punto de congelaci & oacute;n por la noche y la ma & ntilde;ana temprana. Once de los 16 nidos activos al inicio de la tormenta conten & iacute;an polluelos recientemente eclosionados, mientras que los restantes cinco conten & iacute;an huevos. Diez de los 11 nidos con polluelos fallaron para el 23 de junio y un nido que se encontraba a & uacute;n en la etapa de puesta de huevos tambi & eacute;n fall & oacute;. Las hembras asociadas con cada nido fallido construyeron nidos de repuesto en sus territorios originales entre 13-95 m (media = 42 m) de los nidos previos en localidades similares dentro de la cobertura del matorral de Artemisia e iniciaron puestas de remplazo en 7-10 d & iacute;as. El tama & ntilde;o de puesta en nidos de remplazo (n = 10) fue menor (media = 2.9 huevos) que en sus nidos fallidos (media = 3.9 huevos). Los cinco nidos que sobrevivieron produjeron volantones (media = 2.8), as & iacute; como 7 de los 11 nidos de remplazo (media = 2.7), si bien los 11 nidos de remplazo combinados produjeron menos volantones (media = 1.7). Esta perturbaci & oacute;n natural result & oacute; en algo que puede considerarse un costo reproductivo significativo para estos mosqueros, incluyendo (1) un menor tiempo para intentar segundas puestas para la mayor & iacute;a de las parejas siguiendo su reanidaci & oacute;n, independiente del resultado del nido de remplazo y (2) una disminuci & oacute;n en el potencial reproductivo de los intentos de nidos de remplazo. La fecha de la tormenta relativa a la etapa de anidaci & oacute;n fue cr & iacute;tica. Documentamos & uacute;nicamente un caso de doble anidaci & oacute;n en 2025, en el cual una pareja que estaba criando polluelos recientemente eclosionados durante la tormenta tuvo una segunda puesta (tres huevos) despu & eacute;s de que dos polluelos del primer nido se emanciparon, aunque ese segundo nido fall & oacute; sin producir volantones.
Bird-window collisions are a major source of mortality for free-living birds, with estimates of between 1.28 and 3.46 billion bird deaths per year in the United States of America alone. As bird populations continue to decline, any efforts that serve to reduce the number of bird-window collisions can serve as an important conservation tool. While there are multiple products that can be directly applied to windows during the manufacturing process or post-construction, there are also several products that are placed near, but not directly on, window surfaces. Parachute cords can be attached to window frames and are frequently applied with approximately 10 cm (or 4 inches) of space between cords. We investigated whether this window treatment was effective for reducing bird-window collisions that resulted in fatalities, with particular attention toward smaller birds that might theoretically fly between objects spaced approximately 10 cm apart. By consistently surveying a window-rich side of a single college building for 4 years prior to application of parachute cords, and then 3 years post-installation, we were able to evaluate the efficacy of this product under field conditions. We found that cords effectively reduced bird-window collisions for birds of all sizes. Additionally, birds with shorter wing lengths experienced a disproportionate reduction in their number of bird-window collisions. Ruby-throated Hummingbirds (Archilochus colubris) in particular showed the strongest reduction in collisions, dropping from 17 collisions prior to installation of parachute cords to 0 collisions afterward. Thus, parachute cords spaced at approximately 10 cm are effective at reducing bird-window collisions, even for very small birds. Las colisiones de aves contra ventanas son una de las principales causas de mortalidad de las aves silvestres, con estimaciones de entre 1,280-3,460 millones de muertes de aves al a & ntilde;o solo en los Estados Unidos de Am & eacute;rica. A medida que las poblaciones de aves siguen disminuyendo, cualquier esfuerzo que sirva para reducir el n & uacute;mero de colisiones de aves contra ventanas puede constituir una importante herramienta de conservaci & oacute;n. Si bien existen m & uacute;ltiples productos que pueden aplicarse directamente a las ventanas durante el proceso de fabricaci & oacute;n o despu & eacute;s de la construcci & oacute;n, tambi & eacute;n hay varios productos que se colocan cerca de las superficies de las ventanas, pero no directamente sobre ellas. Las cuerdas de paraca & iacute;das se pueden fijar a los marcos de las ventanas y se suelen colocar con una separaci & oacute;n de aproximadamente 10 cm (o 4 pulgadas) entre ellas. Investigamos si este tratamiento de las ventanas era eficaz para reducir las colisiones de aves contra las ventanas, prestando especial atenci & oacute;n a las aves m & aacute;s peque & ntilde;as que, en teor & iacute;a, podr & iacute;an volar entre objetos separados por aproximadamente 10 cm. Mediante un estudio constante de un lado de un edificio universitario con muchas ventanas durante 4 a & ntilde;os antes de la aplicaci & oacute;n de las cuerdas de paraca & iacute;das y 3 a & ntilde;os despu & eacute;s de la instalaci & oacute;n, pudimos evaluar la eficacia de este producto en condiciones reales. Descubrimos que las cuerdas reduc & iacute;an eficazmente las colisiones de aves contra ventanas para aves de todos los tama & ntilde;os. Adem & aacute;s, las aves con alas m & aacute;s cortas experimentaron una reducci & oacute;n desproporcionada en el n & uacute;mero de colisiones contra ventanas. Los colibr & iacute;es Archilochus colubris, en particular, mostraron la mayor reducci & oacute;n en las colisiones, pasando de 17 colisiones antes de la instalaci & oacute;n de las cuerdas de paraca & iacute;das a 0 colisiones despu & eacute;s. Por lo tanto, las cuerdas de paraca & iacute;das espaciadas a aproximadamente 10 cm son eficaces para reducir las colisiones de aves contra ventanas, incluso en el caso de aves muy peque & ntilde;as.
Understanding patterns of abundance and anthropogenic-induced stressors in free-ranging raptors remains challenging due to the difficulty of assessing both abundance and the occurrence of physical lesions in the same populations. However, field photography offers a practical, non-invasive approach to evaluate these traits at specific sites. We conducted 209 h of observation and photographic surveys over four austral winters at two anthropogenic food-rich sites separated by 1,750 km in Argentine Patagonia. We assessed the number of individuals, age structure, and age-specific lesion types and prevalence in overwintering Black-chested Buzzard-Eagles (Geranoaetus melanoleucus). We found that: (1) a minimum of 394 individuals overwintered at these sites; (2) the age structure of counted individuals differed markedly between sites and across time periods, with the northern site (surveyed in 2022 and 2023) slightly skewed toward younger age classes, whereas the southern site (surveyed in 2014 and 2016) was strongly dominated by the oldest age class; (3) 22% (86 of 394 individuals) exhibited lesions, primarily affecting the hindlimbs (e.g. missing legs, digits or talons, and swollen tarsometatarsus-digits joint or digits); (4) among the 86 affected individuals, a total of 102 lesions were documented, yielding a ratio of 1.19 lesions per individual; (5) lesion prevalence was more than twice as high at the southern site (60 of 191 individuals; 31%) compared to the northern site (26 of 203 individuals, 13%); and (6) swollen tarsometatarsus-digits joint or digits was the most prevalent lesion type at both sites, showing no differences among age classes at the northern site, whereas at the southern site it was significantly higher in the oldest age class. Together, these results indicate potential site- or year-specific differences in age structure and age-specific lesion prevalence in overwintering Black-chested Buzzard-Eagles in Patagonia. Comprender los patrones de abundancia y estresores antropog & eacute;nicos en rapaces en libertad sigue siendo un desaf & iacute;o debido a la dificultad de evaluar simult & aacute;neamente la abundancia y la presencia de lesiones f & iacute;sicas en las mismas poblaciones. Sin embargo, la fotograf & iacute;a de campo ofrece un enfoque pr & aacute;ctico y no invasivo para evaluar estos rasgos en sitios espec & iacute;ficos. Realizamos 209 h de observaci & oacute;n y muestreos fotogr & aacute;ficos durante cuatro inviernos australes en dos sitios de origen antropog & eacute;nico con alta abundancia de alimento, separados entre s & iacute; por 1,750 km en la Patagonia Argentina. Evaluamos el n & uacute;mero de individuos, la estructura etaria, los tipos de lesiones y su prevalencia seg & uacute;n clase de edad en & aacute;guilas moras (Geranoaetus melanoleucus) invernando en estos sitios. Encontramos que: (1) un m & iacute;nimo de 394 individuos invernaron en estos sitios; (2) la estructura etaria de los individuos registrados difiri & oacute; marcadamente entre sitios y per & iacute;odos, con el sitio norte (muestreado en 2022 y 2023) ligeramente sesgado hacia clases de edad m & aacute;s j & oacute;venes, mientras que el sitio sur (muestreado en 2014 y 2016) estuvo fuertemente dominado por la clase de mayor edad; (3) el 22% (86 de 394 individuos) present & oacute; lesiones, afectando principalmente las extremidades posteriores (e.g., amputaci & oacute;n de patas, dedos o garras, y articulaciones inflamadas del tarso-metatarso-dedos o de los dedos); (4) entre los 86 individuos afectados se documentaron un total de 102 lesiones, lo que representa una proporci & oacute;n de 1.19 lesiones por individuo; (5) la prevalencia de lesiones fue m & aacute;s del doble en el sitio sur (60 de 191 individuos; 31%) en comparaci & oacute;n con el sitio norte (26 de 203 individuos; 13%); y (6) las articulaciones inflamadas del tarso-metatarso-dedos o de los dedos fueron el tipo de lesi & oacute;n m & aacute;s frecuente en ambos sitios, sin diferencias entre clases de edad en el sitio norte, mientras que en el sitio sur fueron significativamente m & aacute;s frecuentes en la clase de mayor edad. En conjunto, estos resultados indican posibles diferencias espec & iacute;ficas de sitio y/o de a & ntilde;o en la estructura etaria y en la prevalencia de lesiones seg & uacute;n clase de edad en & aacute;guilas moras invernando en la Patagonia.
We report three instances of meadow jumping mice (Zapus hudsonius) using Marsh Wren (Cistothorus palustris) nests at two emergent wetlands in northern Illinois, USA, during the 2024 breeding season. During 2 years of monitoring 220 total nests (2023-2024), we detected meadow jumping mice in three Marsh Wren nests: an adult mouse in an unmodified dummy nest and mouse pups in nests modified with dense shredded grass. All Marsh Wren nests used by mice were elevated, woven around cattails (Typha spp.), and located near open water 23-66 m from the nearest upland habitat. Marsh Wren nest searching took place in 2023-2024 and coincided with small mammal surveys taking place in north-central Illinois. Mouse nest use occurred during a year (2024) of increased meadow jumping mouse detections that followed a 2023 white oak group (white oak Quercus alba, bur oak Q. macrocarpa, swamp white oak Q. bicolor, and overcup oak Q. lyrata) mast event and high spring rainfall in 2024, conditions that we propose may have influenced mouse abundance or limited ground-level nesting sites. Our observations, combined with previous reports of rodents and other taxa using Marsh Wren nests, suggest that Marsh Wrens may facilitate nesting for other species by creating dry, elevated structures within marshes. Our work raises broader questions regarding the frequency and environmental drivers of bird nest use by mice in emergent wetlands. Presentamos tres casos de ratones saltarines Zapus hudsonius que usaron nidos de ratona Cistothorus palustris en dos humedales emergentes del norte de Illinois (EE. UU.) durante la temporada reproductiva de 2024. Durante dos a & ntilde;os de seguimiento de un total de 220 nidos de Cistothorus palustris (2023-2024), detectamos Zapus hudsonius en tres nidos: un adulto de Zapus hudsonius en un nido falso sin modificar y cr & iacute;as de Zapus hudsonius en nidos modificados con hierba desmenuzada densa. Todos los nidos de Cistothorus palustris usados por Zapus hudsonius estaban elevados, tejidos alrededor de totoras (Typha spp.) y situados cerca de aguas abiertas, a una distancia de 23-66 m de la tierra firme m & aacute;s cercano. La b & uacute;squeda de nidos de Cistothorus palustris se realiz & oacute; en 2023-2024 y coincidi & oacute; con censos de peque & ntilde;os mam & iacute;feros en el centro-norte de Illinois. El uso de los nidos por parte de Zapus hudsonius se produjo durante un a & ntilde;o (2024) de m & aacute;s detecciones de Zapus hudsonius, tras un evento de fructificaci & oacute;n masiva de robles blancos (Quercus alba, Q. macrocarpa, Q. bicolor y Q. lyrata) en 2023 y elevadas precipitaciones primaverales en 2024, condiciones que, proponemos, podr & iacute;an haber influido en la abundancia de Zapus hudsonius o haber limitado los sitios de anidaci & oacute;n a nivel del suelo. Nuestras observaciones, combinadas con informes previos sobre roedores y otros taxones que utilizan nidos de Cistothorus palustris, sugieren que estas aves pueden facilitar la nidificaci & oacute;n de otras especies al crear estructuras secas y elevadas dentro de las marismas. Nuestro trabajo plantea preguntas m & aacute;s amplias sobre la frecuencia y los factores ambientales que determinan el uso de nidos de aves por parte de los ratones en humedales emergentes.
Anecdotal evidence and word-of-mouth information can illuminate shifting species occupancy, distributions, and seasonal timings; however, understanding distributional changes requires more comprehensive quantitative approaches. Community science datasets formalize and compile data, enabling the quantitative approach necessary to characterize changing species distributions. We analyzed 13 years of eBird data to characterize the establishment of a bird species (Fish Crow, Corvus ossifragus) with a recently reported range expansion into Maine, a state in the northeastern USA. We found that Fish Crows are restricted to patchy hotspots in southern and coastal Maine, with patches shrinking in geographic size and bird occurrence during the region's cold winter season (November-February). Within-year fluctuations in occurrence, presumably due to migratory behavior, mirrored a more southern population of this species. These results show precisely where and when Fish Crows inhabit Maine, revealing heterogeneous spatial and temporal occupancy patterns that likely reflect the environmental drivers of the recent expansion. Therefore, we explored potential drivers and found that Fish Crows were observed more frequently in developed areas, less forested areas, and after warmer winters. Our analysis contributes to a growing body of work demonstrating the value of community science data to the study of changing species distributions. La evidencia anecd & oacute;tica y la informaci & oacute;n de boca en boca pueden ilustrar los cambios en la ocupaci & oacute;n, distribuci & oacute;n y estacionalidad de las especies; sin embargo, comprender los cambios en la distribuci & oacute;n requiere enfoques cuantitativos m & aacute;s exhaustivos. Los esfuerzos de ciencia comunitaria formalizan y compilan datos, lo que permite el enfoque cuantitativo necesario para caracterizar los cambios en la distribuci & oacute;n de las especies. Analizamos 13 a & ntilde;os de datos de eBird para caracterizar el establecimiento de una especie de ave (cuervo pescador, Corvus ossifragus), con una expansi & oacute;n de su rango de distribuci & oacute;n reportada recientemente en Maine, un estado en el noreste de los EE.UU. Descubrimos que C. ossifragus est & aacute; restringida a & aacute;reas clave dispersas en el sur y la costa de Maine, con & aacute;reas que se reducen en tama & ntilde;o y presencia de aves durante la temporada fr & iacute;a de invierno (noviembre-febrero). Las fluctuaciones interanuales en la presencia, presumiblemente debidas al comportamiento migratorio, se asemejan a una poblaci & oacute;n de esta especie establecida m & aacute;s al sur. Estos resultados muestran con precisi & oacute;n d & oacute;nde y cu & aacute;ndo C. ossifragus habita Maine, revelando patrones de ocupaci & oacute;n espacial y temporal heterog & eacute;neos que probablemente reflejan los factores ambientales que promueven su reciente expansi & oacute;n. Por tanto, exploramos posibles factores y descubrimos que esta especie se observ & oacute; con mayor frecuencia en zonas desarrolladas, zonas con menos bosques y despu & eacute;s de inviernos m & aacute;s c & aacute;lidos. Nuestro an & aacute;lisis contribuye a un creciente n & uacute;mero de trabajos que demuestran el valor de los datos de la ciencia comunitaria para el estudio de los cambios en la distribuci & oacute;n de las especies.
