A long-term, volunteer-based nest-box program for American Kestrels (Falco sparverius) breeding in eastern Pennsylvania was evaluated to identify ways to increase the efficiency of the program and to identify general principles that can be used to improve long-term conservation efforts for other nest-box programs. Between 1993 and 2002, Hawk Mountain Sanctuary volunteers maintained and monitored approximately 270 kestrel nest boxes. Reproductive parameters of kestrels in these nest boxes were similar to those reported in other studies, and kestrels attempted nesting twice in a single year on 11 occasions. Nesting success varied among nest boxes, and productivity was consistently high at some nest boxes and consistently low at others. As a result, approximately half of all nestlings came from the 25% of nest boxes that were used most frequently, and fewer than 7% of kestrels fledged from the 25% of the nest boxes that were used least frequently. Our analysis suggests that volunteer field effort could be reduced by 25% with minimal impact on overall kestrel productivity. Managing for increased conservation efficiency is not inconsistent with effective conservation monitoring and management of kestrels. Our findings have important implications for conservation efforts in which substantial benefits can accrue from more efficient use of limited conservation resources.

Accurate measures of reproductive performance in birds are vital to effective conservation and management of populations. We evaluate the effectiveness of a recently proposed method to estimate reproductive performance based upon behavior of breeding birds during responses to Black-capped Chickadee (Poecile atricapillus) mobbing calls. We examined whether responses of Black-throated Blue Warblers (Dendroica caerulescens) to mobbing calls were related to measures of reproductive performance as determined in a nest monitoring study. We found that individuals that were successful reproducers were more likely to exhibit a response to the mobbing calls. Successfully reproducing individuals were more likely to display evidence of reproductive success (e.g., carrying nesting material, carrying food) when they responded to the mobbing call. Observations of reproductive success, however, depended on the distance of the observation to the nest site of the individual. We conclude that responses to mobbing calls have limited utility for discerning variability in reproductive success among territories. However, if the research objective is to obtain coarse comparative estimates of reproductive success at large spatial scales over which reproductive output is likely to be highly variable, then observations generated by the mobbing playback method may suffice.

The Rufous Hornero (Furnarius rufus: Family Furnariidae), common in southern Brazil, is a territorial, sexually monomorphic bird in which pairs sing duets. This family of birds is known for its lack of sexual dimorphism and for the simplicity of its song types. Here I report that each sex consistently sings a distinct song during the duet: the song starts with both sexes singing identically, followed by a divergence of the female, who slows her singing rate. Also, since both birds pump their wings while singing, at the same frequency as their singing, it possible to see which bird sings at which rate. Sexually dimorphic songs have been observed in other bird species, and suggested in other species in the Family Furnariidae, but this is the first report in which the nature of the song difference is clearly documented. I suggest that many, or all, territorial and sexually monomorphic species of furnariids (and other families, especially suboscines) show similar, consistent sexual differences in song types.

Many studies have reported variation in bird diet composition related to spatial variation in habitat quality and landscape heterogeneity. Most diet analyses involve collection of food items at a sub-sample of available sites. Because individuals at different sites may vary in their diet composition, the description of the diet of a population may depend on which sites are sampled. This potential bias associated with environmental heterogeneity has never been explicitly tested. We used dietary data from a long-term study of an owl population to simulate various scenarios of diet assessment in which the investigator samples food items from various sites without taking into account their variation in quality. The simulations showed that assessment of diet composition was highly dependent on the number and type of sites sampled for food items and that such bias caused by environmental heterogeneity disappeared when food samples were randomly collected at more than 60% of the available sites. Biases in diet description may affect a large number of studies, especially of territorial species in heterogeneous landscapes. Similar biases may apply to the assessment of demographic parameters.

In many birds, it is assumed that conditions for breeding follow a seasonal pattern of improvement and then decline and that for each individual in the population the optimal clutch size is larger when conditions for breeding are more favorable. While this is assumed to be the case for single-brooded species, the situation is more complex for multi-brooded species, which start breeding before the date when their optimal clutch size is greatest and conditions are best for raising nestlings. The seasonal patterns of productivity for multi-brooded species are not generally understood. We compared the clutch size, egg size and weight, and the nesting success of Meadow Pipits (Anthus pratensis) nesting during the early and late stages of the breeding season in Scotland. We also compared the provisioning rates, diet, and number of prey items fed to nestlings. Eggs laid late in the season were significantly larger and heavier than eggs laid earlier in the season. There were generally no differences in diet or provisioning rates of nestlings throughout the season. Despite producing larger eggs late in the season, the probability of such an egg producing a nestling that successfully fledged was 17% lower than an egg laid early in the season. This was mainly due to a significant increase in nest predation late in the season.

Nest predation was the main nest mortality factor for Spotted Towhees (Pipilo maculatus) along the Sacramento River, California, during 1993–2003, followed by cowbird parasitism. From 2001 to 2003, I monitored 161 Spotted Towhee nests and filmed 24 nests using miniature infrared video cameras to identify predators. Daily survival rate was 0.928 for this period. I detected no difference in nest survival between the incubation and nestling stages. Nests with cameras had marginally higher survival rates than those without. I filmed nine nest predation events in 2002 and 2003. Eight of these were upon nestlings, while one was upon eggs. Predators were birds, mammals, and a snake, including the Red-shouldered Hawk (Buteo lineatus), Brown-headed Cowbird (Molothrus ater), Western Scrub-Jay (Aphelocoma californica), a raccoon (Procyon lotor), black or Norway rats (Rattus sp.), two unidentified rodents, and a racer (Coluber constrictor). Many of these predators are associated with agriculture and/or human habitation. I documented two multi-predator events. In both instances, a diurnal partial predation by a bird was followed by a nocturnal rodent predator. Two predation events occurred at the very end of the nestling period. I advise investigators engaged in nest success studies to consider the possibility of partial predation that may reduce a female's overall reproductive output and note that a nest should only be considered successful when direct evidence of fledglings is observed near the nest. I recommend more detailed studies of nest predator composition and the compound effects of Brown-headed Cowbird nest parasitism and “infanticide.”

We radio-tracked eight female Tree Swallows (Tachycineta bicolor) prior to egg-laying in 2000 and 2001. Six females made movements >2 km to evening roosting sites. Females often roosted farther away than the nearest available roost site, they used different roosts on different nights, and during the day they foraged up to 10 km from their nest site. Thus, female swallows move over a large area (103 km²) prior to egg-laying. These widespread movements appear to be unusual among swallows, and they may allow females to survey a large number of extra-pair males.

Bacillus licheniformis, a soil bacterium capable of degrading the β-keratin in feathers, is present in the plumage of some wild-caught birds, but the published carriage rate is quite low. Microbial degradation could be a selective agent leading to the evolution of molt and plumage pigmentation, but we hypothesized that for B. licheniformis to have played an important role in avian evolution, it is likely to occur more widely in bird populations than previously reported. We sampled the plumage of 461 wild-caught birds of eight species. We designed a selective and differential culture method to isolate bacteria with the potential to degrade feathers. Putative feather-degrading bacteria were isolated from 21–59% of the individuals of each of the species tested, for an average carriage rate of 39%. 16S rRNA (rrnA) sequencing of 98 of these bacterial isolates indicated that 69% were Bacillus lichenformis, suggesting that the prevalence of this feather-degrading bacterium is 4 × higher than previously reported. We also hypothesized that interspecific variation in avian plumage, behavior, and habitat may have led to the evolution of host-specific B. licheniformis strains. Fingerprinting of B. licheniformis isolated from Northern Saw-whet Owls (Aegolius acadicus) and Gray Catbirds (Dumetella carolinensis) using REP-PCR demonstrated that for nine owls, one individual carried four different strains and eight individuals carried only one strain. Of 20 catbirds, there was a single strain found on nine birds, but four carried two different strains each.

I report the first nesting records for the Puerto Rican Nightjar (Caprimulgus noctitherus) and Antillean Nighthawk (Chordeiles gundlachii) in Maricao Forest, a montane rain forest of western Puerto Rico. The nightjar nested in leaf litter at the edge of a trail parallel to a eucalyptus plantation (Eucalyptus robusta), at an elevation of 620 m. The nighthawk nested on rocky substrate of a trail in the southern slopes of the forest at an elevation of 460 m. These are the highest elevation nesting records reported for these species in Puerto Rico. The nightjar had a clutch of two eggs and the nighthawk one egg; all eggs hatched successfully. The nightjar had an incubation period of 19 d, consistent with the 18–20 d previously reported.

We used traditional searching, as well as radio-telemetry, to find 125 Wood Thrush (Hylocichla mustelina) nests during 1994–1996 at the Piedmont National Wildlife Refuge in Georgia, USA. We compared daily nest survival rates for 66 nests of radio-marked birds with 59 nests of birds found through systematic searching. By using radio-telemetry, we found Wood Thrush nests in higher elevation pine habitats, in addition to the more usual hardwood forests with moist soils. We found nests of radio-marked birds farther from streams than nests found by systematic searching. Thirty-two percent of radio-marked birds' nests were found at the tops of slopes, compared to 15% of the nests found by traditional searching. In addition, radio-marked birds generally moved up-slope for re-nesting attempts. Although the distribution of nests found with telemetry and searching varied, daily nest survival did not vary between the two groups. Radio-telemetry provided new information about Wood Thrush nesting habitats. We believe radio-telemetry can be a valuable addition to traditional searching techniques; it has the potential to provide a sample of nests free from a priori habitat biases.

Most work on the effects of land-cover change on tropical birds has focused on forest-interior birds because these species are assumed to be the most severely affected by forest loss. However, even species that use human-altered habitat types may be severely affected by forest loss. White-throated Robins (Turdus assimilis) frequently nest in coffee and pasture in southern Costa Rica, although several lines of evidence suggest the species could not exist solely in agricultural habitat. We used radio-telemetry to examine the area and proportion of different habitat types used by adult White-throated Robins. Mean area of use for the tracking period was 0.26 km² and varied from 0.07 to 0.58 km². No robins had areas of use solely in either primary forest or agricultural cover, although individuals were initially captured in both primary forest and a coffee plantation. All areas of use contained some forest, pasture, and coffee or regenerating forest. The mean percentages of the habitat types used by the birds were fairly equal with 30% forest, 33% pasture, and 38% coffee or regenerating forest. Our results, combined with other evidence, indicate that the White-throated Robin uses multiple habitat types but that it may require some threshold level of forest to sustain viable populations.

Sexual selection theory proposes that elaborate male secondary sexual characteristics, including complex song, may increase the attractiveness of males by honestly communicating to females their genetic quality or ability to provide material reproductive resources such as parental care. The Gray Catbird (Dumetella carolinensis) is sexually monochromatic, but males sing complex songs during the breeding season while females do not. We tested the hypotheses that song-phrase versatility and rate of song-phrase production are honest indicators of male parental effort. We predicted that both song-phrase versatility and rate of production would be positively correlated with paternal chick feeding rate. Paternal chick feeding rate was not significantly related to song-phrase versatility, but it was positively and significantly correlated with song-phrase production rate. Thus, song-phrase production rate may serve as a more reliable indicator of male parental quality than song versatility in the Gray Catbird.

Time-lapse video photography has become a valuable tool for collecting data on avian nest activity and depredation; however, commercially available systems are expensive (>USA $4000/unit). We designed an inexpensive system to identify causes of nest failure of American Oystercatchers (Haematopus palliatus) and assessed its utility at Cumberland Island National Seashore, Georgia. We successfully identified raccoon (Procyon lotor), bobcat (Lynx rufus), American Crow (Corvus brachyrhynchos), and ghost crab (Ocypode quadrata) predation on oystercatcher nests. Other detected causes of nest failure included tidal overwash, horse trampling, abandonment, and human destruction. System failure rates were comparable with commercially available units. Our system's efficacy and low cost (<$800) provided useful data for the management and conservation of the American Oystercatcher.

In birds, males and females may benefit by choosing mates based on morphological characteristics correlated with their ability to provide parental care. Our objective was to examine possible relationships between morphological characteristics and the provisioning behavior of male and female Yellow-breasted Chats (Icteria virens). No differences were found in the provisioning behavior of male and female Yellow-breasted Chats. Adult chats provisioned nestlings at higher rates and delivered more biomass at first nests than during later nesting attempts. This indicates that, later in the breeding season, nestling chats may require less energy, perhaps because warmer temperatures lower thermoregulatory costs. No correlations, either positive or negative, between chat morphological characteristics (mass, eye stripe length, tail length, wing chord, tarsus length, and plumage color) and provisioning behavior were noted. Thus, these results do not provide support for either the honest advertisement hypothesis (that predicts a positive relationship between quality and parental care) or the differential allocation hypothesis (that predicts a negative relationship). If mate choice among chats is based on future parental care, the absence of such correlations suggests that characteristics other than those examined in this study may be used by chats. Alternatively, chats may not base mate choice decisions on future parental care, but rather on other features such as territory quality.

We investigated the relationship between migratory restlessness and stored energy reserves in two species of landbird migrants at Braddock Bay, Lake Ontario during spring 1999 and spring 2000. There was no significant difference in the amount of nighttime locomotor activity between lean and fat Swainson's Thrushes (Catharus ustulatus) or White-throated Sparrows (Zonotrichia albicollis) held overnight in activity cages. We found no significant relationships between nocturnal activity level and energetic condition (mass/wing chord) or date of capture. In addition, there were no significant differences in nocturnal activity levels between age groups in Swainson's Thrushes. These results suggest that the migratory restlessness of spring migrants stopping at this site is not strongly influenced by their energetic condition upon arrival, regardless of age or date of passage. Birds nearing the end of their spring migratory route that are very close to their breeding grounds may show decreased levels of migratory restlessness and short stopover durations, independent of energy reserves. When stopping at northerly sites, spring migrants may therefore display distinct differences in stopover behavior and requirements compared to sites used earlier along the spring migratory route.