The Ucayali River is a major tributary of the Amazon, but it narrows considerably toward its headwater at the base of the Andes. This region, the upper Ucayali Valley, is of biological interest for the large number of closely related birds elsewhere separated from each other by major rivers that come into close proximity and potential contact. Between 2006–2011, we conducted the first modern ornithological inventory of the upper Ucayali River and sampled localities in all major avian habitats on either side of the river. We document the continued importance of the Ucayali River as a biogeographic barrier, even at the headwater, but also find that some mixing occurs, both in the form of taxa crossing to the “wrong” bank and in the potential intergradation of distinct forms. We describe the biogeography of birds in the region, characterize the avifaunas of major habitats, and discuss in detail species of particular biogeographical interest.

The process of urbanization and its effects on birds has rarely been documented over long time periods. One exception is a bird count started in the 1860s, when the American ornithologist William Brewster first recorded all the bird species on his property in Cambridge, Massachusetts. Since then, invasive species such as the House Sparrow (Passer domesticus) have been introduced, and the site transformed from an estate surrounded by farmland on the rural edge of the city to a residential neighborhood in the inner core of the Boston metropolitan area. We are fortunate to have additional bird species accounts from around 1900, 1940, 1950, and 1960. In 2012 we repeated the bird survey, thus expanding the time series to 150 years. The changes in the bird community over time have been profound and the data contain a wealth of “stories” about how different species and species guilds have coped. The transition from an agricultural to an urban but also more forested system is clearly visible in the records. Overall, species richness has declined from 26 species in the 1860s to just 12 in 2012. However, this is a slight increase from the low point in the 1960s, and there is evidence that some conditions for birds have improved in the last 50 years.

The historical distribution of Gunnison Sage-Grouse (Centrocercus minimus) in Colorado is described based on published literature, observations, museum specimens, and the known distribution of sagebrush (Artemisia spp.). Historically, Gunnison Sage-Grouse were widely but patchily distributed in up to 22 counties in south-central and southwestern Colorado. The historical distribution of this species was south of the Colorado-Eagle river drainages primarily west of the Continental Divide. Potential contact areas with Greater Sage-Grouse (C. urophasianus) were along the Colorado-Eagle river system in Mesa, Garfield, and Eagle counties, west of the Continental Divide. Gunnison Sage-Grouse historically occupied habitats that were naturally highly fragmented by forested mountains and plateaus/mesas, intermountain basins without robust species of sagebrush, and river systems. This species adapted to use areas with more deciduous shrubs (i.e., Quercus spp., Amelanchier spp., Prunus spp.) in conjunction with sagebrush. Most areas historically occupied were small, linear, and patchily distributed within the overall landscape matrix. The exception was the large intermountain basin in Gunnison, Hinsdale, and Saguache counties. The documented distribution east of the Continental Divide within the large expanse of the San Luis Valley (Alamosa, Conejos, Costilla, and Rio Grande counties) was minimal and mostly on the eastern, northern, and southern fringes. Many formerly occupied habitat patches were vacant by the mid 1940s with extirpations continuing to the late 1990s. Counties from which populations were recently extirpated include Archuleta and Pitkin (1960s), and Eagle, Garfield, Montezuma, and Ouray (1990s).

We conducted a phylogeographic study of the Gambel's Quail (Callipepla gambelii) using sequences of the mitochondrial control region and NADH dehydrogenase subunit 2 (ND2) obtained from 167 specimens including hunter–harvested wings and museum study skins. The Gambel's Quail exhibited strong phylogeographic structure, large genetic gaps, and relatively high levels of haplotype (Hd  =  0.79) and nucleotide diversity (π  =  0.01). Thirty-four Gambel's Quail haplotypes clustered into two distinct haplogroups, with two additional highly divergent haplotypes. Distribution of the haplogroups was not concordant with sampled subspecies or ecogeographic regions; however, the overall distribution of the two haplogroups suggests that the Gambel's Quail may have been isolated in separate refugia of the Chihuahuan and Sonoran deserts during the Pleistocene. Both haplogroups appear to have undergone recent demographic expansion, possibly related to climatic changes associated with the onset of drier conditions in southwestern North America following the end of the Last Glacial Maximum.

Previous studies of northward expansion of breeding ranges of North American bird species have focused on correlated changes in climate and land-use, but very few studies have examined patterns of morphological change within the context of range expansion. We used data from museum specimens to examine geographic and temporal variation in body size of the Red-bellied Woodpecker (Melanerpes carolinus), a species undergoing dramatic range expansion. We plotted georeferenced occurrence data from Christmas Bird Counts (winter distributions going back to the year 1900), USGS Breeding Bird Surveys (summer distributions since 1966), and the holdings of twenty-six natural history museums (year-round distributions since 1867) to document the historic range of M. carolinus in decade increments. Christmas Bird Counts, but not museum specimens, indicate a trend of slow northward expansion beginning as early as the 1910s, and all data sets show rapid expansion to the north and west since the 1950s (average of 0.85° N latitude per decade and 1.06° W longitude per decade). Geographic variation in body size of specimens collected prior to the period of rapid expansion follows Bergmann's rule, with larger birds occurring in northern latitudes. This pattern breaks down in the sample of birds collected after the onset of rapid expansion, suggesting that warming temperatures since the 1950s have enabled northward range expansion in a species previously limited by cold. Birds collected at the northern boundary of their range before 1940 were larger than birds collected in recent decades from the same latitudes, further supporting the hypothesis that Red-bellied Woodpeckers have been released from a former ecological or physiological constraint in the face of climate warming.

Numerous studies have shown that testosterone (T) increases singing rates of passerine birds, but much less is known about the influence of T on non-song vocalizations, particularly in non-passerine species. Woodpeckers (order Piciformes) give several non-song vocalizations in a variety of social contexts throughout the year, including whinny and pik calls. We gave free-living male Downy Woodpeckers (Picoides pubescens) subcutaneous T implants during the non-breeding period to determine whether the incidences of these calls were greater among experimental males and their female partners compared to control males and females. We also tested whether calls were given more or less often when pair members were spatially proximate, and whether T treatment affected this pattern. Both call types were more likely given when pair members were nearby (<40 m), and this was true regardless of T treatment. Surprisingly, both males with T-implants and their female partners showed significantly lower incidences of whinny calls than control birds, and the female partners of T-implanted males also gave fewer pik calls. We attributed these patterns to the possible effect of T on non-vocal behaviors that influenced the social relationship between members of a pair.

In seasonally breeding birds annual changes occur in hormone production by the hypothalamic-pituitary-gonadal (HPG) axis as individuals transition between breeding and non-breeding condition. Typically, some external environmental cue induces the observed changes; changes in day length, corresponding to change of seasons, are a strong cue for HPG axis activity in many species. Some species use cues other than day length as their primary initiator of breeding, and a number of light-sensitive species incorporate other cues to initiate breeding. Northern Cardinals (Cardinalis cardinalis) exhibit individual variation in when breeding begins and circulating testosterone is present throughout the year. Chemical tests of HPG axis responsiveness indicate that many individuals have an activated HPG axis as early as December. Here we use GnRH injections to assess whether individuals with active HPG axes prior to the winter solstice and increasing day lengths, may be influenced to initiate breeding by low temperatures experienced at the time of GnRH challenge. We found that while a significant number of individuals had active HPG axes prior to the winter solstice, there was no effect of low temperatures. We suggest that broader environmental patterns and additional cues may be influential to breeding in cardinals as opposed to only immediate temperature changes.

Noise pollution poses a significant obstacle to vocal communication. Songbirds rely on acoustic signals for mate choice and territory defense, and masking of these signals can have negative fitness consequences. Prior investigations reveal that birds mitigate the negative effects of acoustic masking by increasing their signal amplitude or by singing with higher minimum frequencies. In this study, we evaluate the responses of male Pacific Wrens (Troglodytes pacificus) to natural ambient noise (ocean surf) and anthropogenic noise (highway traffic) in Pacific Rim National Park Reserve, B.C., Canada. Pacific Wrens, known for their complex songs, are specialists of old-growth forest. We hypothesized that Pacific Wrens would compensate for the effects of ambient noise in their environments through modifications to their songs that enhanced their transmission properties. Recognizing that longer, higher frequency, and more complex signals propagate better in noisy environments, we predicted that Pacific Wrens would increase the length of their songs, the length of the syllables within their songs, the number of syllables per song, and the minimum frequency of their songs. Recordings of 52 territorial Pacific Wrens showed that proximity to highway traffic noise had a significant effect on song duration but no significant effect on any of the other measured variables. Pacific Wrens that were recorded near the shoreline, however, sang songs with longer syllables, and higher intra-individual variation in song duration. Number of syllables, syllable minimum frequency, and song duration did not vary with distance from the shoreline. We conclude that natural and anthropogenic noise sources influence the singing behavior of Pacific Wrens.

The Golden-winged Warbler (Vermivora chrysoptera) is one of the most rapidly declining vertebrate species in the Appalachian Mountains. It is the subject of extensive range-wide research and conservation action. However, little is known about this species' breeding ecology in high-elevation pasturelands, a breeding habitat with conservation potential considering the U.S. Natural Resource Conservation Service's Working Lands for Wildlife program targeting private lands in the Appalachian Mountains. We located 100 nests of Golden-winged Warblers in pastures in and around the Monongahela National Forest in West Virginia during 2008–2012. Daily nest survival rate (mean ± SE  =  0.962 ± 0.006), clutch size (4.5 ± 0.1), and number of young fledged per nest attempt (2.0 ± 0.2) and successful nest (4.0 ± 0.1) fell within the range of values reported in other parts of the species' range and were not significantly affected by year or the presence/absence of cattle grazing. Classification tree analysis revealed that nests were in denser vegetation (≥52%) and closer to forest edges (<36.0 m) and shrubs (<7.0 cm) than random locations within the male's territory. Successful nests had significantly more woody cover (≥9%) within 1 m than failed nests. Our results suggest that cattle grazing at 1.2–2.4 ha of forage/animal unit with periodic mowing can create and maintain these characteristics without interfering with the nesting of Golden-winged Warblers. High-elevation pasturelands may provide a refuge for remaining populations of Golden-winged Warblers in this region.

Forest openings, or canopy gaps, are an important resource for many forest songbirds, such as Cerulean Warblers (Setophaga cerulea). We examined canopy gap selection by this declining species to determine if male Cerulean Warblers selected particular sizes, vegetative heights, or types of gaps. We tested whether these parameters differed among territories, territory core areas, and randomly-placed sample plots. We used enhanced territory mapping techniques (burst sampling) to define habitat use within the territory. Canopy gap densities were higher within core areas of territories than within territories or random plots, indicating that Cerulean Warblers selected habitat within their territories with the highest gap densities. Selection of regenerating gaps with woody vegetation >12 m within the gap, and canopy heights >24 m surrounding the gap, occurred within territory core areas. These findings differed between two sites indicating that gap selection may vary based on forest structure. Differences were also found regarding the placement of territories with respect to gaps. Larger gaps, such as wildlife food plots, were located on the periphery of territories more often than other types and sizes of gaps, while smaller gaps, such as treefalls, were located within territory boundaries more often than expected. The creations of smaller canopy gaps, <100 m², within dense stands are likely compatible with forest management for this species.

Amami Thrushes (Zoothera dauma major) are endemic birds distributed on Amami-Oshima Island in southwestern Japan. The population is considered to have declined during the latter half of the 20th century, mainly because of deforestation. I investigated the breeding habitat of Amami Thrushes in order to contribute to conservation efforts for these endangered birds. Field surveys showed that the thrushes prefer old-growth broad-leaved forests for breeding habitat. Both male and female parents cared for the nestlings, and most food items delivered for nestlings were earthworms, which were more abundant on the forest floor in older forests than in younger forests. Nests were placed on forks of large tree branches, rock ledges, and epiphytic ferns in middle to low strata of the forest. Older forests contained more large trees than younger forests, and epiphytic ferns were distributed in old-growth forests. The thrushs' preference for old-growth forests as breeding habitat was explained by the abundance of food and nesting resources in that environment. These results suggest that the preservation of old-growth broad-leaved forests should be given top priority if Amami Thrushes are to be protected.

We describe attributes of Northern Saw-whet Owls (Aegolius acadicus) during fall migration using 167,774 records from the U.S. Bird Banding Laboratory for central and eastern North America from 1929–2010. We describe movement among 18 geographic regions using records of 1,444 birds captured and recaptured between 1 September and 31 December of the same year. These data show little exchange between western Lake Superior and eastern North America. The direction of movement within a region was strongly influenced by large water bodies, varied greatly among regions, and showed high dispersal in the absence of shorelines of large water bodies. We used recent banding data to analyze population demographics from northwestern Minnesota to the coast of Maine in the north, and from southern Minnesota and southern Wisconsin to southern Appalachia and the mid-Atlantic coastal region in eastern United States. The weighted mean proportion of Hatch Year (HY) birds declined significantly from 63% in northwestern Minnesota to 42% in southern Minnesota/southern Wisconsin and from 70% in northern Ontario to 48% in southern Appalachia. Annual variation in the proportion of HY birds showed little correlation between eastern and central origin sites but moderate correlation within each of these regions. We define irruptions as years when the proportion of HY birds is 15% or greater than the weighted mean for each site, a level that occurs once in 4 years on average but at irregular intervals. We determined a very high correlation between the proportion of HY birds banded in northeast of Lake Ontario and the abundance of small mammals, suggesting a close relationship between food supply and reproductive success.

The distinct rufous and gray color-morphs of the Eastern Screech-Owl (Megascops asio) have long intrigued ornithologists. Eastern Screech-Owls range across the eastern half of the United States, where the morph ratio varies from >70% rufous birds in the center of the range to <30% rufous at the periphery. Although the adaptive significance of polymorphism is, in general, poorly understood, careful mapping of the morph-frequency and determination of ratio clines is a first step toward understanding this phenomenon. In this paper, I examine the distribution of Eastern Screech-Owl color-morphs in Iowa, which lies in the northwestern part of the species' range. I collected 519 records of Iowa screech-owls from museum curators, wildlife rehabilitators, bird-banders, and bird watchers. For all records combined, 41.0% were rufous morphs, 55.7% were gray morphs, and 3.3% were intermediates. For all birds of known sex, 44.7% (21/47) of males and 57.6% (34/59) of females were rufous; the difference was not statistically significant, but the results are consistent with a trend in other studies suggesting that females are more likely than males to be rufous. The percentage of rufous screech-owls increased clinally from west to east across Iowa, but did not change from north to south. Because annual precipitation exhibits a longitudinal pattern in Iowa and annual temperature exhibits a latitudinal pattern, this suggests that the morph ratio pattern in Iowa is influenced more by precipitation than by temperature. Based on records dating 1880–2003, the percentage of rufous birds decreased from the early to later decades of the 20th century. The range-wide distribution of morph ratio clines fits a model where rufous morphs are better-adapted at the center of the range but gray morphs are selected for toward the periphery.

Birds use song to communicate with conspecifics, and song can influence both intra-sexual competition and inter-sexual mate choice. Some birds produce repertoires consisting of hundreds of songs while others produce a single song type. For species with a single-song repertoire, there are varying levels of inter-individual variation which can be the result of environmental, genetic, and physiological factors. Male Snow Buntings (Plectrophenax nivalis) typically produce a single song type, and while syllable sharing occurs between individuals, many researchers have anecdotally noted the individuality of each male's song. To investigate this long-held assertion, we performed a detailed bioacoustic analysis of male Snow Buntings recorded in the Canadian Arctic. We use canonical discriminant analysis to provide quantitative evidence confirming that male Snow Buntings sing individually distinctive songs. Furthermore, we present the first evidence that some Snow Buntings exhibit inter-annual variation in song structure; while songs remain consistent within each year, two males changed their song type between years. Inter-individual variation in song content can have important behavioral implications, because it facilitates individual recognition and can affect individual fitness.

We present the first confirmed case of hybridization between a Lesser Black-backed Gull (Larus fuscus) and Herring Gulls (Larus argentatus) in North America (outside of Greenland). We discovered a Lesser Black-backed Gull × Herring Gull pair on Appledore Island, Maine in 2007. Nuclear DNA analysis indicated that the Lesser Black-backed Gull was the genetic parent of the chicks from 2008 to 2011. The offspring have not returned to breed, so we do not know if they are fertile. Increasing numbers of observations of Lesser Black-backed Gulls, including putative Lesser Black-backed Gull × Herring Gull hybrids along the Atlantic coast, indicate that Lesser Black-backed Gulls may be in the process of colonizing North America. If so, additional hybridization with Herring Gulls is likely in areas of overlap.

We applied a Monte Carlo approach to test for both individual and group level laterality preferences in neck looping by American Flamingos (Phoenicopterus ruber ruber) at rest. We found no evidence of individual or group-level preferences, contrary to the results of previous studies. In the present data, the appearance of bias tended to decrease as the number of observations increased, suggesting that apparent lateral bias may be largely because of stochastic error. Pair members tended to loop the neck to the same side on the same day to a greater extent than expected by chance, implying that social factors can act contrary to any individual lateral preference that may exist in this species.

Piping Plovers (Charadrius m. melodus) were banded in eastern Canada, in the Gulf of St. Lawrence (Gulf) region, including the Magdalen Islands (Québec), New Brunswick, Newfoundland, northern Nova Scotia and Prince Edward Island, and the southern Nova Scotia (sNS) region from 1998–2003, and recaptured and/or resighted from 1999–2007. Return rates of banded individuals were greater for adults than juvenile birds, likely reflecting the higher survival and site fidelity of this age class. The best-fit model explaining differences in annual dispersal distance included age class (P < 0.001), region (P  =  0.004) and the interaction of age class and region (P  =  0.074). Juvenile dispersal movements in the Gulf (median: 28.0 km, range: 0.4–306.3 km) were greater than in sNS (median: 18.6 km, range: 6.5–74.8 km), but adult movements in sNS (median: 4.0 km, range: 0.01–70.7 km) were greater than in the Gulf (median: 0.5 km, range: 0.01–298.6 km). While some annual dispersal movements in the Gulf were large enough to cover the distance between both regions (>225 km), these movements only represented 1% of all observations and none involved movements between the Gulf and sNS. The lack of movement between regions, and previous studies documenting differences in population dynamics and habitat use, suggests that two distinct breeding populations of Piping Plovers exist in eastern Canada. Future management of the species should consider the distinct conservation needs of both populations and recognize that local efforts may not result in regional population increases because of small dispersal distances in eastern Canada, and, potentially, in other populations in North America. At this time, the small sNS population may be particularly vulnerable to extirpation, as the potential for dispersal from nearby populations appears limited.

We studied Greater Roadrunners' (Geococcyx californianus) habitat use during spring and summer of 2011 in the Red Rolling Plains of west Texas. We captured 10 roadrunners (one male and nine females) and fitted each with a 10-g backpack style radio-transmitter. Roadrunners were relocated 2–4 times per week from February–August. We used these data to build a logistic regression model to better understand the vegetative and topographic features important to roadrunners during the nesting season. The initial data set consisted of 30 random and 30 used locations. The best model showed both percent rock and percent litter to be higher at used locations and correctly classified 88% of the sites. Evaluation of the model with an additional 30 random and 30 used locations maintained significance of both the model and variables and correctly classified 83% of sites. Both variables were associated with the location's mesa ridge slopes. Litter dominated locations under shrubs on the ridge tops and slopes and likely provided security from predators, nest sites, and relief from extreme summer temperatures. Percent rock cover characterized locations on ridge tops and slopes which provided perch sites, travel lanes, and foraging sites where the roadrunners could find basking prey.

We investigated whether Northern Mockingbirds (Mimus polyglottos) alter their nocturnal foraging behavior in areas with artificial light at night. We observed mockingbirds after sunset at six study sites that varied in levels of artificial light. We hypothesized that birds at the parking lot and residential sites would feed their nestlings later at night because of light pollution. The average time past sunset that birds across all sites continued to feed nestlings was positively correlated with average light level around the nest. Mockingbirds in the parking lot fed their nestlings ∼15 mins later than those in the other sites, suggesting that this abundant urban species can exploit light pollution.

The provisioning behavior of male and female songbirds varies among species, but most species exhibit biparental care. Our objective was to examine the provisioning behavior of male and female Indigo Buntings (Passerina cyanea), a species where males are reported to provide little or no parental care. Nests (n  =  16) were video-taped during the 9-day nestling period and provisioning rates of adult buntings subsequently quantified. Provisioning rates of female buntings varied with nestling age, with 7–9-day old nestlings fed at higher rates than 1–6-day old nestlings. This increase was likely because of the increasing energy demands of nestlings. Male buntings provisioned nestlings at only three of 16 nests (18.8%), and primarily on days 7–9 post- hatching. Given the apparent relationships among paternal care, mating systems, and habitat characteristics, high-quality habitat may be an important factor contributing to reduced levels of paternal care by male buntings, along with opportunistic polygyny. Highly productive habitats with plentiful food resources may allow one parent to successfully care for young. Although habitats occupied by Indigo Buntings are apparently of sufficient quality to have favored a reduction in male parental care, variation in territory quality may require the contributions of some males to enhance nestling survival.

Seed preferences of wild birds may be a result of factors such as bill and seed morphology, handling time, nutritional content of the seed, and foraging behavior of the bird. To examine factors influencing seed choice of 10 species of birds that regularly visit bird feeders in the United States and Canada, we collected data on bird visits, bill size, seed size, and nutritional content of seeds for 10 seed types commonly used in bird seed blends. The presence of an outer hull, protein content, and the ratio of bill volume to seed volume were the most important variables determining seed choice. Fiber and fat content were less important. Results from this study help us understand why birds that use feeders use the seed types they do, and ultimately, may improve the composition of seed species and individual seeds found in bird food blends.

Laughing Falcons (Herpetotheres cachinnans) are common, medium-sized falconids that occur throughout the Neotropical region and marginally in the Nearctic American continent. There is little data on their breeding biology with the only information available based on scattered records. Here, we report data on 11 nests of H. cachinnans from the Pantanal, Brazil, including four in nest-boxes, between 2007–2008. The breeding season occurred between July–December, which is in accordance with the few records for this region. Records of two eggs or nestlings were found in 28% (n  =  3) of nests, while the remaining 72% (n  =  8) had one egg or nestling. The eggs were rounded and buff with brown markings or dark brown or purplish brown with darker markings. The hatchlings, even when a few days old, are pale buff overall in plumage with the distinctive black mask, typical of the adults. An undescribed vocalization of the nestling was recorded, which is similar to an uncommon vocal type emitted by the adults when disturbed. The study reveals novel data on the use of nest-boxes and on the breeding biology of the species, and reinforces the importance of such studies on its conservation.

Populations of Red-throated Caracaras (Ibycter americanus) have been extirpated or are in serious decline throughout Middle America. We describe the first nest outside South America and provide only the third nest description for the species. We observed four adults and one immature Red-throated Caracara provide cooperative care to a single nestling at a nest in a region dominated by pine-oak forest in departamento (dpto.) de Olancho, Honduras. The nest was a bowl-shaped structure of branches and pine needles located at the mid-canopy level of a pine tree (Pinus oocarpa), and is the first nest described in an ecosystem other than humid broadleaf forest. We report the first observation of adult Red-throated Caracaras using a nest as a short-term food cache, as well as the first observation of Red-throated Caracara taking fledgling birds as prey. Although Red-throated Caracaras are considered a resident of humid broadleaf forest, we suggest that pine-oak forests may be an important habitat for the species in the northern portion of its range.

We studied the reproduction patterns of Squacco Herons, Ardeola ralloides, during 2009–2010. This study was carried out in two colonies located at Ichkeul National Park (37.184992 N, 9.633758 E) and Lebna Dam (36.744161 N, 10.916569 E), in northern Tunisia. We determined the reproductive performance of the species, and investigated the relationship between reproductive parameters and nest characteristics (height and diameter). We registered successful nesting, with mean clutch size of 4.51 ± 0.85 for both years combined. Hatching success was 3.67 ± 1.07 eggs hatched/nest and fledging success reached 3.06 ± 1.28 young/nest. All reproductive parameters varied between years. The diameter and the height of nest had no effect on the clutch size, the initial brood size, or the final brood size at each site. We estimated the body condition index (BCI) and the growth curves of developing nestlings from repeated measurements of body mass, tarsus, head and bill length. The last chicks (rank four) to hatch had lower (BCI) and growth rates than the first, the second, and the third hatched chicks. These results stress the need for further protection measures be undertaken at Lebna Dam. Accessibility to the site should be highly controlled by the managers of Tunisian wetlands.

The correction of a long standing error in what was thought to be the location of the Milestown School where Alexander Wilson, the Father of American Ornithology, taught from 1796 to 1801.