We used two metrics, occupancy and relative abundance, to study forest stand characteristics believed to be important to a threatened seabird that nests in old-growth forests, the Marbled Murrelet (Brachyramphus marmoratus). Occupancy refers to murrelet presence or absence based on observed bird behaviors, while relative abundance refers to categories of low, medium, and high numbers of bird observations per survey in a forest stand. Within the murrelet's nesting range in California and southern Oregon, we measured habitat and climatic variables in all old-growth stands surveyed for murrelets between 1991 and 1997. The two bird metrics produced similar results. In California, murrelets most often occupied, or were abundant in, redwood (Sequoia sempervirens) stands with large trees (>100 cm diameter at breast height) located on gentle, low-elevation slopes or on alluvial flats close to streams. In stands of the less flood-tolerant Douglas-fir (Pseudotsuga menziesii) in southern Oregon, murrelets most often occupied, or were abundant on, gentle, low-elevation, west-facing slopes that were not close to streams. Murrelets tended to use areas farther from roads. The important climatic requirements for murrelet stands in both states were cool temperatures and high amounts of rainfall.

Basic nesting information on grassland passerines is needed for improving grassland bird management. Among the information needs are (1) the suitability of nesting habitat, (2) periods during the breeding season in which birds are most vulnerable to disturbances, and (3) how to fit grasslands into a prioritization scheme for conservation. Comparisons of nesting parameters among grassland species will help identify important management considerations. We describe and compare nest-site characteristics, nesting phenology, clutch size, hatching and fledging success, and brood parasitism by Brown-headed Cowbirds (Molothrus ater) for three grassland passerine species nesting in tallgrass prairie of northwestern Minnesota and southeastern North Dakota. During 1998–2002, we found 793 Clay-colored Sparrow (Spizella pallida), 687 Savannah Sparrow (Passerculus sandwichensis), and 315 Bobolink (Dolichonyx oryzivorus) nests. These species differed in many aspects of their breeding ecology. Clay-colored and Savannah sparrows initiated their nests almost 2 weeks earlier than Bobolinks, with peak nesting occurring in June. Clutch size was lower (3.77 ± 0.03 SE) for Clay-colored Sparrows than Savannah Sparrows (4.13 ± 0.05) and Bobolinks (5.25 ± 0.08). The number of host eggs hatched per nest was higher in Bobolinks (3.46 ± 0.20) than in Clay-colored Sparrows (2.52 ± 0.09) and Savannah Sparrows (2.41 ± 0.11), but the number of young fledged per Bobolink nest (1.97) was similar to that of Savannah Sparrows (2.01). Clay-colored Sparrows fledged only 1.35 host young per nest. Mayfield nest success was higher for Savannah Sparrows (31.4%) than for Clay-colored Sparrows (27.4%) or Bobolinks (20.7%). The main cause of nest failure was nest predation: predation in Clay-colored Sparrows (47.9%) was higher than in Savannah Sparrows (33.5%) but similar to Bobolinks (41.8%). Brood parasitism was lower in Clay-colored Sparrows (5.1%) than in Bobolinks (10.8%), and intermediate (6.7%) in Savannah Sparrows. Compared with most other studies, grassland bird nests in our study area were more successful and less frequently parasitized; thus, northwestern Minnesota and southeastern North Dakota appear to provide important breeding habitat for grassland birds.

Observations by local naturalists may provide valuable records of phenological events with which we can measure the response of species to climate change. To test this idea, we examined the records of a dedicated naturalist who has been observing bird arrivals, plant flowering, butterfly appearance, and frog calling on her farm in Middleborough, southeastern Massachusetts. From her 1970 to 2002 records, we extracted data on first observations of spring phenological events for 24 species—650 observations in all. Over that time, average annual local temperatures rose by 2.0° C. Twenty-two species showed earlier activity, with 5 of the 16 bird species now arriving significantly earlier in the year than they did 30 years ago. Twenty-two species responded to warming temperatures, with 4 species (two birds, one frog, and one plant) showing statistically significant earlier activity in years with warmer temperatures. The other 18 species showed similar trends, but they were not statistically significant.

Determining the sizes and characteristics of home ranges among American Crows (Corvus brachyrhynchos) in spring/summer is essential for understanding the importance of this species in the transmission of West Nile virus. In late spring, summer, and early fall of 2002, we radio-tracked 45 American Crows to estimate their movements and habitat preferences in urban and adjacent agricultural habitats in east-central Illinois. The 95% minimum convex polygon home ranges averaged 9.6, 6.7, and 6.4 km² for hatch-year, sub-adult, and adult crows, respectively. Proportional habitat use was investigated at two scales: (a) at the study site scale, there was a preference for low- to medium-density urban habitat and avoidance of forested habitat; and (b) at the home range scale, there was a preference for agricultural cover and avoidance of high-density urban habitat.

We examined eight marking techniques designed specifically for use on newly hatched Red-winged Blackbird (Agelaius phoeniceus) nestlings (colored polishes applied to either the culmen or the hallux; colored elastic, plastic, or band-aid bands applied to the tarsus; stains applied to either the superciliary down or the tarsus; and superciliary down clipping) to determine which technique had the shortest application time and longest retention. Application times and retention rates varied between marking techniques, but this did not affect nestling growth or survival. Clipping of superciliary down feathers had the shortest application time and the highest retention rate of all techniques studied. This technique, however, is only applicable to species whose newly hatched young have superciliary down. Other techniques examined had comparably short application times, but were not retained for the entire nestling period.

We present information on the breeding biology and nest-site characteristics of the western subspecies of the Chipping Sparrow (Spizella passerina arizonae) in montane ponderosa pine (Pinus ponderosa) forests of the Colorado Front Range. We located 83 nests during the summers of 1999–2002. The earliest egg date was 23 May and young fledged as late as 11 August. Nests were typically placed in needle clusters on outer branches of ponderosa pines. Mean canopy cover at nest sites was 50%. We observed no differences in nest placement or nest-site microhabitat between successful and unsuccessful nests. The nesting cycle lasted approximately 30 days, including 4 nest-building days, 3 egg-laying days, 14 incubation days, and 9 brooding days. Nests with known outcomes fledged a mean of 1.67 young from a mean clutch of 3.08 eggs. At least 27 nests (32.5%) were depredated, making predation the primary cause of nest failure. Of 42 successful nests, 5 (11.9%) were parasitized, although at least two Chipping Sparrows and one Brown-headed Cowbird (Molothrus ater) fledged from each parasitized nest. Both parasitism rates and nest success are highly variable among populations in this species.

Male Black-capped Chickadees (Poecile atricapillus) sing for several minutes prior to dawn during the breeding season. In northeastern Colorado, dawn singing was associated with male-female interactions rather than male-male interactions; males did not approach one another during the chorus. Males sang until female arrival, at which point they attempted copulation. During copulation attempts, males always uttered strings of variable sees and nearly always attached gargles to these strings. All gargles terminated in an acoustically similar, low-pitched, buzzy syllable.

From 1984 through 1987, we studied aggressive responses of Prairie Falcons (Falco mexicanus) to species intruding into their nesting territories in southwestern Idaho (52 nesting attempts, 613 days, 9,085 hr). Prairie Falcons responded aggressively most frequently to Common Ravens (Corvus corax; 49% of encounters), followed by Red-tailed Hawks (Buteo jamaicensis; 24%), Golden Eagles (Aquila chrysaetos; 7%), Turkey Vultures (Cathartes aura; 4%), Northern Harriers (Circus cyaneus; 2%), American Kestrels (Falco sparverius; 1%), and bobcats (Lynx rufus; 1%). The frequency of aggressive responses toward intruders was similar for males and females, except in the case of American Kestrels and bobcats. Aggressive responses of nesting Prairie Falcons to intruders may be related to predator deterrence, competition for nest sites, stage of the nesting cycle, food availability, and sexual size dimorphism of falcons.

I present the first description of the nest, eggs, and nestlings of the Castelnau's Antshrike (Thamnophilus cryptoleucus). During June and July of 2003, I observed three nests of T. cryptoleucus in riverine habitats along the Río Amazonas, downstream from Iquitos, Departamento Loreto, Perú. The nests were deep, thin-walled cups suspended from the surrounding vegetation 1–3 m above the ground. The clutch size was two, and the eggs were cream-colored with reddish-brown markings. I found two nests on islands in the Río Amazonas and one nest on the mainland, providing evidence that T. cryptoleucus is not exclusively restricted to river islands. Two nests were in river-edge forest dominated by Cecropia, and one was in second-growth scrub next to a banana plantation, suggesting some tolerance of anthropogenic disturbance. All three nests were active during the period when the annual floodwaters were receding. Nest placement, structure of the nest, clutch size, and appearance of the eggs were all similar to those of the closely related Blackish-gray Antshrike (Thamnophilus nigrocinereus) and are typical of the genus.

Much confusion exists over the proper way to handle nest-fate data collected after the fledge date when using the Mayfield method. I provide a simple numerical example showing how use of these data can bias estimates of daily survival probability, and present a likelihood function demonstrating that nest-fate data collected after the fledge date do not contribute any information for parameter estimation, except in a seldom-realized special case. Consequently, it is recommended that under the Mayfield model, nest-fate data collected after the fledge date be discarded.

I observed a Western Scrub-Jay (Aphelocoma californica) consume a Golden-cheeked Warbler (Dendroica chrysoparia) nestling and a Brown-headed Cowbird (Molothrus ater) nestling in northwestern Travis County, Texas, in May 1995. During a 4.5-hr period after brood destruction, warbler adults repeatedly brought insects to the depredated nest, and during each visit they appeared to search for the nestlings in the nest area and adjacent trees while carrying the insects. When the jay subsequently returned to the nest to take an unhatched egg, the female warbler performed a distraction display. My observations indicate that, in some cases, parental feeding behavior and nest defense can continue for a short time after brood loss.

We examined age differences in wing loading, aspect ratio, wing span, and tail area in a sample of 117 Red-tailed Hawks (Buteo jamaicensis) captured at the Cedar Grove Ornithological Station, Wisconsin, during 1979–1987. Adults had significantly wider wings, lower aspect ratios, shorter tails, and smaller tail surface areas than juveniles. Red-tailed Hawks showed fewer age differences in aerodynamic characteristics than Sharp-shinned Hawks (Accipiter striatus), probably because of differences between the two species in the pursuit and capture of prey. Sharp-shinned Hawks take birds from above ground or after a brief chase, often in dense vegetation. Sharp-shinned Hawks require more aerial agility (ability to make rapid twists and turns) than is necessary for Red-tailed Hawks, which capture prey on the ground, usually after a glide or flight from an elevated perch.

Baseline demographic data are lacking for most tropical forest birds, particularly from undisturbed habitats. During the 2003 breeding season, we documented the productivity of Abbott's Babbler (Malacocincla abbotti), a sedentary insectivorous passerine, on a 30-ha permanent forest plot in northeastern Thailand. We found 17 active nests of 13 breeding pairs, for which the Mayfield estimate for overall nesting success was 0.36 ± 0.13 SE. Breeding started in mid-January, a month earlier than previously recorded. Despite a relatively long period of post-fledging parental care, at least five pairs were double-brooded.

We present the first description of a nest of the Ocellated Antbird (Phaenostictus mcleannani), an understory species that ranges from southeastern Honduras to northwestern Ecuador. The open-cup nest was found in June 2002, in the Republic of Panama, and was located on the leaf litter between the buttresses of a Virola surinamensis tree. The nest contained two ovoid, whitish eggs with reddish-brown speckles and longitudinal streaks.