Because of the patchiness of their habitat, its perceived low conservation value, and tendency to burn, bamboo-specialist birds are vulnerable to habitat loss. We documented the habitat use and foraging strategies of Celeus obrieni, Kaempfer's Woodpecker, in forested cerrado (savanna) with patches of the bamboo Guadua paniculata near Pium, Tocantins, Brazil. We surveyed for C. obrieni, measured vegetation structure at 30 sites where it was detected and 23 where it was not detected, then compared vegetation characteristics through nonmetric multidimentional scaling and one-way analysis of similarity to determine whether C. obrieni was specializing on particular habitat characteristics. We studied the species' foraging and compared the abundance of prey in drilled and nondrilled stems to evaluate its dietary specialization. All sites with C. obrieni had large, tall stands of G. paniculata, indicating habitat specialization. Drilling most frequently on large, dry stems from 2 to 4 m off the ground, the woodpeckers consumed ants, mainly Camponotus depressus and Azteca fasciata, which colonize the internodes of bamboo stems. Habitat specialists are more vulnerable to habitat loss or alteration but can serve as indicator species for the reaching of conservation goals. Large stands of forested cerrado with patches of bamboo should be conserved for C. obrieni to be maintained. The patchiness of bamboo forest may impede dispersal of C. obrieni.

In 2003 and 2004 I investigated the relationship between patch area and number of avian bamboo specialists among 13 patches of Guadua bamboo habitat in southeastern Peru. In these patches, specialists were sensitive to area at local spatial scales. The structure of communities of bamboo specialists was nested, meaning species present in depauperate patches were almost always present in richer patches. Richness of specialist species was positively correlated with the size of the patch. My results indicate that prior estimates of populations of bamboo specialists based on remotely sensed images of vegetation may be underestimates because several specialists were present in small patches difficult to detect in remotely sensed images.

Semelparous woody bamboos flower fairly synchronously and in clocklike fashion after many years, providing abundant and nutritious seeds. However, this resource is ephemeral, localized, and unpredictable from the perspective of birds that feed on those seeds. Birds specializing on bamboo seeds track this food source and are nomadic. We recorded Temminck's Seedeater (Sporophila falcirostris) at 29 localities and the Buffy-fronted Seedeater (S. frontalis) at 23 localities in Argentina, Paraguay, and southeastern Brazil. In these species, nomadism is unassociated with any seasonal factor: birds may persist year round over several consecutive years if the seed supply is constant enough. Most occurrences and all breeding records were related to masting of bamboo; records of isolated birds away from seeding bamboo must represent individuals searching for bamboo patches. We report winter breeding of these species for the first time and demonstrate that the supply of bamboo seeds is the main limitation to their breeding. On a broad spatiotemporal scale, large-seeded bamboos (e.g., Guadua spp.) may function as strong population pumps, small-seeded bamboos (e.g., Chusquea spp.) as maintenance stations. Both species fed mostly on bamboo seeds, occasionally on bamboo flowers, and rarely on alternative food sources. They consumed insects frequently and occurred in mixed-species flocks, especially during autumn and winter. Creation of a network of protected areas is essential to preserve bamboo patches that flower at different times and localities in sufficiently large quantities to guarantee the long-term survival of the peculiarly dynamic populations of bamboo seedeaters.

A post-flowering die-off of bamboo in an established bird-census plot afforded us an opportunity to investigate the response of bamboo-dwelling birds to a natural transformation of their habitat. In 1984 and 1985 SR and JT generated spot maps for an 80-ha plot in terra firme forest near the Cocha Cashu Biological Station, Manu National Park, Peru. Two mapped bamboo patches in the plot totaled approximately 30 ha. In 2001 and 2002, the bamboo flowered and died. In 2009, JS revisited the plot and generated spot maps for the former bamboo patches and adjacent forest. By 2009, trees had grown up in the erstwhile bamboo patches, creating stands of second growth surrounded by mature forest. Twelve species of bamboo specialists were no longer present but almost no new species had invaded. We conclude that the maintenance of high bird diversity in western Amazonian forests does not depend on the spatial heterogeneity caused by dying off of bamboo. This result contrasts with, but does not contradict, previous research demonstrating the importance of some disturbances such as treefalls opening gaps to avian biodiversity in neotropical forests. A few bamboo specialists, including the Brown-rumped Foliage-Gleaner (Automolus melanopezus), Goeldi's Antbird (Myrmeciza goeldii), Flammulated Pygmy-Tyrant (Hemitriccus flammulatus), and Dusky-tailed Flatbill (Ramphotrigon fuscicauda), persisted in the die-offs. Their choices of microsites suggested that vegetation structure rather than plant-species composition is an important determinant of habitat suitability for these specialists.

Marine radar is a tool widely used in the study of bird migration, but in most cases it cannot identify detected objects to species. For this reason airspeed is used as one of the main criteria to separate birdlike from insectlike targets, but this criterion has not been tested outside the temperate regions where it was developed. We used a theoretical approach for calculating minimum-power speeds (V_mp) and maximum-range speeds (V_mr) of birds and insects to estimate an interval of airspeeds from which an appropriate value of the criterion can be selected and to propose a criterion based on flight speed for the Isthmus of Tehuantepec in southern Mexico. This approach, with data from 36 species of insects and 60 of passerines either known to occur or similar to species occurring in southern Mexico, found that although V_mp of insects and birds overlaps at 5.5 m sec^-1, birds generally fly faster than insects. After combining our results with data from the literature, we conclude that the best airspeed to be used as criterion for distinguishing birdlike from insectlike targets lies within the range of 5.5–9.0 m sec^-1 and that 7 m sec ^-1 is an appropriate airspeed for our study area. These airspeeds are applicable in southern Mexico and in regions where birds and insects have physical dimensions similar to the species addressed in our study.

This study investigated seasonal differences in fat deposition and nutritional status of migrating passerine birds at an important stopover site on the south shore of Lake Ontario. Birds were captured during spring and autumn stopovers, and their plasma metabolites were measured as indicators of refueling rates (plasma triglyceride) and nutritional state (plasma uric acid). Catharus thrushes had higher plasma triglyceride and lower plasma uric acid in autumn than in spring, whereas Red-eyed Vireos had higher plasma triglyceride in spring than in autumn, but no seasonal differences in plasma uric acid. There were no seasonal differences in plasma triglyceride concentrations in White-throated Sparrows (Zonotrichia albicollis) and Blackpoll Warblers (Setophaga striata), although White-throated Sparrows had plasma uric acid higher in spring than in autumn, suggesting they were consuming more protein than were those captured during autumn migration. These data suggest that songbirds use this site for refueling during both spring and autumn, but substantial seasonal differences in fat and protein metabolism indicate seasonal shifts in habitat use by some species. Results of this study emphasize the importance of considering seasonal differences in food availability and interspecific differences in stopover site use when these sites are managed to provide high-quality habitat across seasons for a range of songbird species.

The population of Tundra Swans (Cygnus columbianus columbianus) breeding on the lower Alaska Peninsula represents the southern extremity of the species' range and is uniquely nonmigratory. We used data on recaptures, resightings, and recoveries of neck-collared Tundra Swans on the lower Alaska Peninsula to estimate collar loss, annual apparent survival, and other demographic parameters for the years 1978–1989. Annual collar loss was greater for adult males fitted with either the thinner collar type (0.34) or the thicker collar type (0.15) than for other age/sex classes (thinner: 0.10, thicker: 0.04). The apparent mean probability of survival of adults (0.61) was higher than that of immatures (0.41) and for both age classes varied considerably by year (adult range: 0.44–0.95, immature range: 0.25–0.90). To assess effects of permanent emigration by age and breeding class, we analyzed post hoc the encounter histories of swans known to breed in our study area. The apparent mean survival of known breeders (0.65) was generally higher than that of the entire marked sample but still varied considerably by year (range 0.26–1.00) and indicated that permanent emigration of breeding swans was likely. We suggest that reductions in apparent survival probability were influenced primarily by high and variable rates of permanent emigration and that immigration by swans from elsewhere may be important in sustaining a breeding population at and near Izembek National Wildlife Refuge.

Predation is the primary source of mortality of dabbling duck nests, so a key aspect of parental investment is defending the nest from predators. The hen's presence on the nest is widely considered to be a good measure of nest defense; an incubating female camouflages the nest and may physically deter nest predators. Parental-investment theory suggests that investment should increase with the reproductive benefits expected from the current clutch of eggs. We used nest-temperature loggers to study how the rhythms of waterfowl incubation changed after the nest was partially destroyed by a predator. Contrary to the expected-benefits hypothesis, we found that hens significantly increased their investment after partial clutch loss: they took fewer recesses from incubation per day and extended their incubation by more than 200 min after a partial depredation. We suggest that when predators pose little risk to the incubating adult, those hens unable or unwilling to abandon a nest after partial clutch loss will increase parental investment to obtain at least some reproductive benefits.

A Brownian bridge movement model (BBMM) is a relatively new concept that estimates the path of an animal's movement probabilistically from data recorded at brief intervals. A BBMM assumes that locations are not independent, whereas the “classical” kernel-density estimator (KDE) assumes they are. We estimated BBMM home ranges for 11 Black Vultures (Coragyps atratus) and 7 Turkey Vultures (Cathartes aura) equipped with satellite transmitters near Marine Corps Air Station Beaufort, South Carolina, from October 2006 to November 2008. The 95% BBMM home ranges (95% BBMM) of the two Black Vultures that traveled >100 km from the capture site were 833 and 2111 km²; of the nine that did not travel as far, 95% BBMM ranged from 33 to 778 km² and averaged (± SE) 243 ± 76 km². The majority of Turkey Vultures (n = 6) traveled >100 km from the capture site with 95% BBMM ranging from 923 to 7058 km² and averaging 3173 ± 1109 km². We also estimated KDE home ranges, using newer satellite technology for comparison with previous studies. Overall 95% KDE ranged from 17 to 16066 km² for the Black Vulture and 988 to 36257 km² for the Turkey Vulture. The concept of an animal's home range has evolved over time, as have home-range estimators. With increasing use of satellite telemetry, application of BBMM can greatly enhance our understanding of home ranges, migration routes, seasonal movements, and habitat-use patterns of wild birds over large and often remote areas.

Life-history theory suggests that delayed maturation is beneficial to birds when costs of breeding early in life are high. We compared selected aspects of the biology of male Cooper's Hawks (Accipiter cooperii) that began breeding at 1 year of age (SY males) vs. males that began breeding ≥2 years of age (ASY males) in an effort to elucidate what renders breeding of SY males rare. Of the 732 males of known age whose breeding we studied over 32 years (1980–2011) 13 (2%) were SY and 719 (98%) were ASY During this period, the incidence of breeding of SY males changed markedly, as 12 of the instances of breeding of SY males were recorded in the first half of our study, only 1 in the latter half. We suggest that SY males could acquire nest sites more readily in the first half of the study when the breeding population of ASY males was apparently lower. Males breeding in their second year were on average similar in size to ASY males but were molting more extensively than were ASY males. ASY males lived longer than males breeding in their second year, and maximum lifetime production of young was greater, so SY males may have sacrificed greater longevity for breeding early. A strategy of facultative breeding in response to the constraints of higher numbers of older breeding males and restraints of trade-offs in energy allocation may explain why SY male Cooper's Hawks rarely breed.

The family Rallidae is a distinct, species-rich group of birds, many of which are exceptional at long-distance colonization. Six of the ten species in the genus Rallus are distributed in the Americas. Among these, R. longirostris and R. elegans have an interwoven taxonomic history that reflects their weak phenotypic differentiation, the multiplicity of allopatric, morphologically distinct populations, a long zone of secondary contact in the eastern U.S. along which hybridization occurs, and apparent ecological “replacement” of each other in marshes of varying salinity. We used mitochondrial and nuclear gene sequences, the latter generated from next-generation sequencing, to infer phylogenetic relationships in the complex from a sample of 70 individuals collected throughout their distribution. Average levels of mitochondrial and nuclear divergence were relatively low (<2%) both within and between the species. The complex is composed of three distinct biogeographic groups: (1) eastern North America and the Caribbean, (2) South America, and (3) western North America, including Mexico. Our results indicate that R. elegans as currently recognized is paraphyletic, with birds of the highlands of Mexico sister to R. longirostris of California. Rallus elegans of eastern North America and Cuba is sister to R. longirostris from eastern North America and the Caribbean. This paraphyly, along with the reproductive isolation of the ecologically divergent R. elegans and R. longirostris in the eastern United States, supports splitting the complex into five morphologically and genetically distinct species.

Avian foraging activity during daytime peaks after dawn and before dusk. The relative importance of each period of intensive foraging on the accumulated intake varies by species, individual, and day. We studied the relative importance of each period from direct observation of radio-tagged Common Cranes (Grus grus) during winter at a site of stopover and wintering in Spain. After a mathematical model was fitted, accumulated intake showed a typical anti-sigmoid shape, with greatest increases of intake after dawn and before dusk. The rise of accumulated intake decelerated until 50% of the day length, when the trajectory inflected and accelerated according to the fitted model. The trajectory of accumulated intake in territorial families that foraged in small home ranges with food predictably available but the cost of vigilance high decelerated until 20% of the day length, then accelerated for the rest of the day. In flocking nonterritorial cranes the inflection point was delayed until 60% of the day length, as expected since flocking cranes foraged in larger home ranges with food less predictable and the cost of vigilance lower. The inflection point was delayed in early winter and advanced in late winter. The changes in the inflection points of the functions for accumulated food intake may be straightforwardly applied to daily foraging routines of other species whose rates of intake may be recorded.

In expanding populations, individuals may increasingly be forced to use sites of relatively low quality. This process, named the “buffer effect,” was previously described for the Black-tailed Godwit (Limosa limosa islandica) in its use of nonbreeding sites in Great Britain and of breeding areas in Iceland. On the basis of diet analyses from droppings and stable isotopes, we describe a new case for the expanding French wintering population of the Black-tailed Godwit, an expansion accompanied by a drastic change in feeding strategy. In the 1990s, Black-tailed Godwits started using intertidal mudflats at Ile de Ré, where they eat the rhizomes of seagrass (Zostera noltii) rather than the customary shellfish (Macoma balthica) eaten at both the preferred (initial) site (Aiguillon Bay) and the area occupied last (Yves to Marennes-Oléron bays). Individually color-marked godwits appeared faithful to both diet type and site, suggesting a cost of a change of strategy. This represents a first case of rhizome-feeding in shorebirds, and it exemplifies a case of carnivorous birds occupying a new site shifting to herbivory.

Along with breeding and migration, molt is one of the most energetically expensive components of a bird's annual cycle. Auklets (tribe Aethiini) are apparently unique among the Alcidae in that flight-feather molt and breeding overlap. We compared the degree of overlap of primary molt with breeding in the Least Auklet (Aethia pusilla) at four colonies in varying oceanographic environments: Kiska Island (Aleutian Islands, Alaska, 52°N), St. George Island (Pribilof Islands, Alaska, 56°N), St. Paul Island (Pribilof Islands, 57°N), and Cape Ulyakhpen (Chukotka Peninsula, Russia, 64°N). We hypothesized that the onset and speed of feather replacement should be related to latitude or sea-ice dynamics. Flight-feather molt commenced during incubation with up to four primaries replaced by the end of chick rearing. At Kiska, we found no difference in molt rate between adult breeders and nonbreeders, but subadults started molt after adults and were more variable in when they started primary molt. At higher latitudes adult auklets replaced their first four primaries faster and initiated molt later although the length of the breeding season was similar. The increased energetic requirements of Least Auklets breeding and molting at higher latitudes are supported by the cold Anadyr Current, which advects lipid-rich oceanic copepods (Neocalanus spp.). In the Least Auklet and other members of the Aethiini, sequential primary molt, rather than the simultaneous molt typical of other alcids, may be possible because of auklets' lower body mass, lower wing loading, mass loss at hatching, and foraging on highly abundant prey.

We present a prototype monitoring strategy for estimating the density and number of occupied burrows of burrow-nesting seabirds. We use data and management questions from Washington State as an example that can be applied to burrow-nesting seabirds at single- or multi-island scales. We also demonstrate how habitat assessments can be conducted concurrently. Specifically, we compared the density and occupancy of burrows of the Rhinoceros Auklet (Cerorhinca monocerata) at nesting colonies in the California Current and the Salish Sea and in the 1970s, 1980s, and today. We estimated 36 152, 1546, and 6494 occupied burrows on Protection and Smith islands (Salish Sea), and Destruction Island (California Current), respectively. Our estimates for the Salish Sea are 52% greater than those from the 1970s and 1980s, while that for the California Current is 60% less than that of 1975. This suggests that the Salish Sea population has increased, despite greater human effects on that ecosystem. However, some of the estimated changes between the periods could be the result of methodological and analytical differences. To address these issues we recommend an unbiased and representative sampling approach (stratified random) and an approach for optimally allocating the samples among strata within and among islands, depending on the scale of the question being addressed. Optimally allocating the sample would save a great deal of field effort; using this approach, we achieve relatively high power (>0.80) to detect moderate changes (20%) sampling hundreds of fewer plots than in a sample not optimally allocated.

Northern Saw-whet Owls (Aegolius acadicus) breed throughout the boreal forest of North America, but little is known about their population trends or distribution within this region. Analysis of stable hydrogen isotopes (δ²H) in feathers can delineate origins of a variety of avian migrants, but raptors are reported to have high intra-feather isotopic variance and mean δ²H values higher than predicted from δ²H isoscapes specific to raptor feathers, making assignment of geographic origin sometimes difficult. We examined the applicability of δ²H analysis of saw-whet owl feathers to delineating origins of migrants and to assessing differences in the migratory behavior of adult and young owls by using multiple generations of feathers from owls captured during fall migration at the Delta Marsh Bird Observatory, Manitoba, 2006–2007. Values of δ²H in saw-whet owl feathers were higher than predicted from a δ²H isoscape specific to raptor feathers and from patterns of movements inferred from analysis of band recoveries. This effect was pronounced in adults, while values of δ²H in feathers of hatching-year owls fell primarily within the range predicted for the boreal forest northwest of Delta Marsh. Significant differences in δ²H values among feather generations suggest that physiological or behavioral differences between adults and young give rise to greater ²H enrichment in adult feathers. These results indicate that current δ²H isoscapes for feathers cannot be used to track adult saw-whet owls reliably and further research into the mechanisms of ²H enrichment in owl feathers is required.

We investigate phylogenetic relationships among the foliage-gleaners of the genera Automolus, Hyloctistes, Hylocryptus, and Clibanornis (Furnariidae) by means of DNA sequences of mitochondrial and nuclear genes. The genus Automolus is not monophyletic because A. rubiginosus and A. rufipectus are more closely related to Hylocryptus and Clibanornis and because Hyloctistes is nested within the main Automolus clade. Hylocryptus erythrocephalus and H. rectirostris are not sister species; the former is part of the A. rubiginosus complex, whereas the latter is sister to Clibanornis dendrocolaptoides. Two species, A. infuscatus and A. rubiginosus, are not monophyletic, indicating the need for further taxonomic revision. On the basis of our phylogenetic analyses and of quantitative assessments of phenotypic variation, we propose a new classification for Automolus and allies, including the description of a new subgenus.

In many bird species, double brooding (producing a second brood after successfully rearing a first) is a common reproductive strategy that can greatly increase reproductive output. However, the proportion of breeding pairs that produce a second brood varies considerably from year to year. Here, we examine how environmental factors such as weather patterns and individual factors such as clutch size, the female's body mass, and date of breeding affect the rate of double brooding in a population of the Western Bluebird (Sialia mexicana) in New Mexico. More pairs tended to produce second broods in years in which freezing ended earlier and there was warm, dry weather during the breeding season, but this pattern was apparent only when we excluded years with wildfires from the analysis. In addition, pairs that bred earlier were more likely to produce a second brood, and in these pairs females tended to be heavier. Thus both the length of the breeding season and the weather during that time influence rates of double brooding, and an individual's condition can affect whether or not it produces a second brood. Knowledge of how weather patterns influence birds' reproductive effort can help scientists predict how bird populations will respond to changing weather in the future.

Guilds of species that share ecological similarities or recent ancestors are often the basis of studies concerning habitat partitioning. An interesting result of many of these studies is that means of partitioning in one area of sympatry may be different from those in disjunct areas of overlap. Here, we quantified the differences in habitat preference of two forest thrushes in the southern Appalachian Mountains. The Hermit Thrush (Catharus guttatus) has recently expanded its breeding range south along the spine of the Appalachians into the spruce—fir forests of Virginia, North Carolina, and Tennessee. There, it shares breeding habitat with the congeneric Veery (C. fuscescens), previously the only forest thrush breeding in this area. We used several multivariate analyses of habitat variables within both species' territories to understand how these species partition the available habitat and to test if these means of partitioning are similar to those found by other studies. We calculated the niche overlap to be 0.248, indicating that the habitat structures preferred by these two species are highly distinct. Hermit Thrushes generally preferred forest with a high degree of canopy closure, high percent coverage of leaf litter, and low percent cover below 3.0 m. Veery territories generally had a high percent of cover between 0.5 and 3.0 m (i.e., the shrub layer) and less canopy closure than the Hermit Thrush plots. Our data suggest that the Hermit Thrush is expanding south because it is attracted to the maturing of the spruce forests in this region.

Survival of fledgling songbirds can be influenced by habitat characteristics at multiple spatial scales, and identifying the relative influence of habitat characteristics at the micro (immediately surrounding fledglings) and meso (level of stand or cover type) scales is important for management and conservation planning. We modeled survival of fledgling Ovenbirds (Seiurus aurocapilla) in managed forest in north-central Minnesota by using micro-scale and meso-scale habitat characteristics and nestlings' mass as explanatory variables. Meso-scale variables (e.g., use of logging roads and distance to cover types other than those used for nesting) better explained fledgling Ovenbirds' survival than did nestlings' mass or micro-scale variables, including ground cover, litter depth, vegetation density, and food availability. Crossing of logging roads had the strongest relationship with survival of fledgling Ovenbirds: survival of fledglings that crossed roads was 50% lower during the first 8 days after fledging and 33% lower 9–16 days after fledging than that of fledglings that did not cross roads. We conclude that although micro-scale habitat characteristics can influence fledgling Ovenbirds' survival, meso-scale characteristics have a much stronger effect. We believe nestlings' mass had little influence on survival because mass may be a poor indicator of body condition, and regardless of condition most predation occurs before fledglings are capable of eluding predators. Because of the association between logging roads and fledglings' reduced survival, we suggest that reclamation of abandoned logging roads, a process underway on many federal lands, could have a positive effect on populations of ground-dwelling forest birds in managed forests.

Sex ratios of adult birds are frequently skewed, but in few species is the sex ratio of offspring also skewed. Adult females, however, should modify their offspring's sex ratio and invest more in the sex with the greatest future reproductive potential. We investigated the relationship between nestlings' morphology, timing of reproduction, and sex ratios in broods of the Saltmarsh Sparrow (Ammodramus caudacutus), a species with extreme levels of multiple paternity: males provide no parental care and sex ratios of adults may be highly skewed. By molecular methods, we sexed 157 nestlings from 52 Saltmarsh Sparrow nests in Connecticut over 2 years. Their sex ratio was significantly skewed toward males (59%) and did not vary with brood size, but this imbalance is insufficient to fully explain the reported skew in adults' sex ratio. Just prior to fledging, male nestlings were larger than female nestlings, which may suggest that they are more costly to produce. Survivorship is greater in nests initiated immediately after high spring tides, but we found no relationship between sex-ratio bias and the risk of tidal flooding. Female Saltmarsh Sparrows consistently produce male-skewed broods, regardless of their nests' risk of flooding, suggesting that male nestlings are a consistently better investment. The Saltmarsh Sparrow appears to be an exception to the pattern typical of birds, in which the population of adults is skewed toward males but the sex ratio of offspring is balanced. These results may help to refine future age-specific population projections for this species of high conservation concern.

I describe primary replacement in molt-migrant Painted Buntings (Passerina ciris) captured during molt in northern coastal Sinaloa. Primary replacement is rapid, start dates vary substantially by year, and, especially in females, start and end dates for the molt overlap broadly in some years. The earliest adult females to initiate primary replacement start at the same time as adult males, but many females initiate molt very late, apparently because their mates desert late broods to migrate and molt early. These issues conspire to make traditional estimates of the duration of primary replacement invalid; thus, I calculate molt duration as D = L/G, where L is the summed length of independently grown primary and G is the primaries' growth rate. Adult females replace their primaries in 30.3 (SE = 4.27) days, adult males in 34.3 (SE = 2.99) days. For 54 hatch-year birds that were molting when captured I calculated start dates for the eccentric molt to show, for the first time for any species, that young birds that initiate this partial replacement of primaries later in the season replace fewer feathers. The intensity of the primary molt in adult females, the sexual conflict that results in many females initiating molt much later than males, and recent habitat changes in coastal northwest Mexico, all conspire to suggest that the cause of the decline in the Midwestern breeding population of the Painted Bunting is likely related to recent increases in the mortality of adult females during their annual post-breeding molt.

We examined two measures of immune function (bactericidal capacity of the blood plasma and a pro-inflammatory response to an injection of phytohemagglutinin) and baseline levels of corticosterone in wild adult male Brown-headed Cowbirds (Molothrus ater) to determine whether the size of the song repertoire, a fixed or “static” signal, can be linked to current condition. We hypothesized that static signals and immune function are positively correlated with males' quality because high-quality males should exhibit relatively large sexual signals and also maintain high levels of immune function. In contrast to our primary prediction, we found that song-repertoire size and bactericidal capacity were negatively correlated. We also found that repertoire size and corticosterone levels were positively correlated and that there was no relationship between corticosterone level and either measure of immunity. The positive correlation between corticosterone level and repertoire size suggests that males with larger repertoires expend more energy than do males with smaller repertoires and that the negative correlation between repertoire size and bactericidal capacity is mediated via activity levels, because corticosterone does not appear to suppress immune function directly. If repertoire size indicates a male's quality, these results imply that the level of immune function of high-quality males is not high at all times and that increased energy expenditure related to breeding may draw resources away from immune function.

Accurate analysis of trends in densities estimated from survey data depends on selection of a model that fits the data. When such analysis uses data recorded at different times in the same area but from different transects, then the target species' density and spatial heterogeneity become an issue. It is possible, even in the absence of environmental change, that one set of transects may underestimate or overestimate the density entirely on the basis of location. The resulting risk is that the density estimated earlier may falsely indicate a decline or an increase when compared to the densities estimated later. We investigate this problem for trend analysis of two species of endangered Hawaiian birds at Hakalau Forest National Wildlife Refuge, island of Hawaii. Assertions based on Bayesian regression, and accepted by the U.S. Fish and Wildlife Service, purportedly indicate increases in the density of the endangered Hawaii Akepa (Loxops coccineus coccineus) from 1977 to 2007 and of the endangered Hawaii Creeper (Oreomystis mana) from 1987 to 2007. Here we show, at four study sites spanning the south—north axis of the refuge, that capture rates per mist-net hour of both species declined significantly and the 1977 transects used underestimated density because of location. We submit that the main reason for the differences between our piecewise regression and Bayesian regression is the inappropriate use of Bayesian regression. Analysis by the appropriate model indicates that since 2000 all Hawaiian birds at Hakalau Forest National Wildlife Refuge have been declining.