We describe the first verified nests, eggs, and nestlings of the Nightingale Reed-Warbler (Acrocephalus luscinia), an endangered species endemic to the Mariana Islands, Micronesia. Nest composition, nest dimensions, and eggs were studied on the island of Saipan. Nests were located within three habitat types: upland introduced tangantangan (Leucaena leucocephala) forest, a native mangrove (Bruguiera gymnorrhiza) wetland, and a native reed (Phragmites karka) wetland. Nesting substrates included five native and two introduced tree species and one native reed species. Nests were composed primarily of dry vine stems, needle-like branchlets of ironwood (Casuarina equisetifolia), and tangantangan petioles. Nests were compact to bulky in construction and were secured to a forked arrangement of branches or stems. The background color of eggs ranged from white to cream to ivory-buff. Eggs were spotted, speckled, and blotched with gray, brown, black, and rust colored markings. Clutch size was 2–4, with a mode of two. Hatchlings were altricial with closed eyelids and devoid of natal down with dark gray to black skin. Nestlings examined prior to fledging resembled the adult plumage, except for the lack of the yellow supercilium found in adults. The nests and eggs have some characteristics similar to those of other Acrocephaline warblers found throughout Micronesia and Polynesia.

We reviewed the status of the breeding marine birds on San Benedicto Island, Mexico, based on >100 years of published observations and seven of our own surveys conducted between 1978 and 2000. We found that there have been marked changes in the island avifauna with two main trends evident. First, a volcanic eruption destroyed much of the island in 1952. The Wedge-tailed Shearwater (Puffinus pacificus; estimated breeding population 1,000 pairs), Townsend's Shearwater (Puffinus auricularis; probable breeder, small numbers), and Red-footed Booby (Sula sula; 60 pairs) historically had much larger populations, but they apparently never fully recovered from the eruption. The Masked Booby (Sula dactylatra; 2,185 pairs), however, has become much more abundant perhaps due to changes in the vegetation. The second trend is that within the last three decades at least two, and possibly four, species from the central Pacific have colonized the island. The Laysan Albatross (Phoebastria immutabilis; 12 pairs) started breeding in the late 1980s; Black-footed Albatross (Phoebastria nigripes; 1 pair) in 2000. Red-tailed Tropicbirds (Phaethon rubricauda; probable breeder, 10 pairs) may have started breeding in the 1980s, and at least some of the breeding Brown Boobies (Sula leucogaster; 300 pairs) are from central Pacific populations. The reason(s) for this influx of central Pacific species is unknown, but likely involves changes in the marine environment. Other breeding species include the Red-billed Tropicbird (Phaethon aethereus; 200 pairs), Nazca Booby (Sula granti; 50 pairs), Great Frigatebird (Fregata minor; 165 pairs), and Magnificent Frigatebird (Fregata magnificens; 5 pairs).

New information on the vocalizations and behavior of populations of the Olive-backed Foliage-gleaner (Automolus infuscatus), along with analysis of biometric and plumage characters, reveal that it actually consists of at least two biological species: a form that is restricted to southeastern Amazonia, south of the Amazon and east of the Rio Madeira; and a group that occupies much of the remainder of humid lowland forest in Amazonia and the Guianan region. The southeastern form, although cryptically similar morphologically to other southern Amazonian subspecies of Automolus infuscatus, is highly differentiated in all vocal characters. Its distribution overlaps the Rondônia, Pará, and Belém centers of endemism. The remainder of the populations currently considered part of the infuscatus group are further differentiated into two subgroups: a northern Guianan group and a southern-western group, the member taxa of which are weakly differentiated from one another, but which differ from members of the other group in plumage, biometric, and vocal characters. The significance of these differences with respect to species limits may depend on the species concept used. Current evidence would support recognition of the two groups as separate phylogenetic species in addition to the southeastern species, but is considered insufficient to support recognition of more than two species under a biological species concept.

With the designation of Nelson's Sharp-tailed Sparrow (Ammodramus nelsoni) and Saltmarsh Sharp-tailed Sparrow (A. caudacutus) as species of high conservation priority in the northeastern United States, the need to document fully their abundance, distribution, and the extent of range overlap has become increasingly important. We surveyed saltmarshes in coastal New England for both species from 1997 to 2000. The current overlap zone extends from Parker River, Massachusetts, north to Weskeag River, Maine, which expands the previously reported range overlap of 48 km to 208 km. Among the 49 sites surveyed within the current overlap zone, both species were present at 25 sites. It is possible that the species have experienced range expansion over the last several decades, especially the Nelson's Sharp-tailed Sparrow. Our findings indicate that the nominate subspecies of the Saltmarsh Sharp-tailed Sparrow warrants the greatest conservation concern given its limited geographic range, a potentially expanding hybrid zone with A. n. subvirgatus, and the potential for habitat degradation from an oil spill associated with the urban/industrial centers of the Northeast.

We present historic and contemporary information on the distribution and abundance of Buff-breasted Sandpipers (Tryngites subruficollis) in South America. Historic information was collated from the literature, area ornithologists, and museums, whereas contemporary data were derived from surveys conducted throughout the main wintering range in Argentina, Uruguay, and Brazil during the austral summers of 1999 and 2001. Variable circular plot sampling was used to estimate population densities. During 1999, the highest concentration of Buff-breasted Sandpipers in Argentina was in southern Bahía Samborombón (General Lavalle District) and areas north of Mar Chiquita coastal lagoon. During 2001, the highest concentrations in Brazil were at Ilha da Torotama and Lagoa do Peixe National Park. During 1999 and 2001, the highest concentrations of Buff-breasted Sandpipers in Uruguay were found along three lagoons (Laguna de Rocha, Laguna de Castillos, and Laguna Garzón) bordering the Atlantic Ocean. Population densities (birds/ha) of Buff-breasted Sandpipers were 0.11 (95% C.I. = 0.04–0.31) in Argentina, 1.62 (0.67–3.93) in Brazil, and 1.08 (0.37–3.18) in Uruguay. High turnover rates at survey sites, due to the formation of large, mobile flocks, contributed to moderately large confidence intervals around our population density estimates. Nevertheless, compared with historic accounts of Buff-breasted Sandpipers, our survey data indicate the population size of this species has declined substantially since the late 1800s and contemporary information suggests the species has continued to decline during the past three decades. Buff-breasted Sandpipers were found almost exclusively in pasturelands and appear to depend heavily upon intensive grazing by livestock, which maintain suitable short grass conditions. We discuss the need for protection of critical areas and proper range management to ensure appropriate habitat remains available for the species, and provide suggestions for future research needs.

This study examined the effectiveness of treating ticks (Ornithodoros capensis) infesting nests of Eastern Brown Pelicans (Pelecanus occidentalis carolinensis). The number of immature ticks on nestling pelicans was significantly less in treated than in control nests. Nest abandonment also was less in treated nests; however, in severely infested nests, treatments did not prevent abandonment. Nesting success and hematocrit measurements did not differ significantly between control and treated groups.

We assessed edge avoidance, area sensitivity, and the relationship between local and regional forest cover for nesting Red-eyed Vireos (Vireo olivaceus) in 13 forest fragments (1–2,353 ha in size) in southcentral Ontario, Canada. Red-eyed Vireo territories and nests were not significantly farther from the edge than random points in any of the forest fragments, and there was no relationship between the probability of a male pairing and the distance of the territory from the edge of the forest fragment. The density of singing males and the probability of a male being paired increased significantly with increasing local forest cover within a 2-km radius of a study site, but not with forest fragment area or regional forest cover within a 10-km radius. Nest success was low and the probability of a nest being parasitized by the Brown-headed Cowbird (Molothrus ater) or successfully fledging ≥1 host young did not vary with distance of the nest from the forest edge or with any of our area or forest cover measures. Red-eyed Vireos did not display edge avoidance nor did they appear to be area sensitive within our study region, but there was a positive relationship with the amount of local (2-km radius) forest cover. Maintaining localized regions with high forest cover has been recommended on numerous occasions for the conservation of area sensitive species; our results suggest high forest cover also may benefit species that do not appear to be area sensitive.

Little research has examined the ecology of mixed species flocks of migrant and resident landbirds during migratory periods. We studied habitat use and behavior of mixed species insectivorous landbird flocks during fall migration in central Pennsylvania. From late August to early October, 1998 and 1999, 220 flocks were observed for 30-min periods in six forest habitat types: mature forest interior, mature forest edge, mature forest agricultural edge, mature suburban forest, pole stage forest, and shrub/sapling stage forest. Sixty species were recorded in flocks that contained 2–24 species each (mean = 9.25 ± 0.29 SE). Flocks contained 2–181 individuals (mean = 22.12 ± 1.18 SE). Flocks in the six habitats had 49–61% Nearctic-Neotropical migrant individuals, 5–15% temperate migrants, and 23–37% residents. Abundance and species richness of migratory guilds (Nearctic-Neotropical migrants, temperate migrants, and resident species) within flocks were highest in structurally heterogeneous habitats (especially forest edge habitat) and were lowest in homogeneous pole stage forest. Of nine migrant species whose abundance varied significantly among habitats, six had highest abundance in flocks in forest edge habitat: Blue-headed Vireo (Vireo solitarius), Red-eyed Vireo (V. olivaceus), Blue-gray Gnatcatcher (Polioptila caerulea), Chestnut-sided Warbler (Dendroica pensylvanica), Black-throated Green Warbler (D. virens), and Magnolia Warbler (D. magnolia). Resident parids (Black-capped Chickadee, Poecile atricapillus, and/or Tufted Titmouse, Baeolophus bicolor) occurred within 82% of flocks and were observed leading 68% of these flocks. Movement rate (m/min) of flocks varied among habitats with flocks in edge-dominated habitats (forest edge, forest agricultural edge, and suburban forest) tending to have slower movement rates than in pole stage forest and forest interior, suggesting that food availability may have been greater in edge-dominated habitats. Consistently high species richness and abundance of migrant guilds and individual species strongly suggests that structurally diverse forest edge habitats were selected and provided relatively high quality stopover habitat for landbirds during fall migration.

We studied the dispersion of Northern Waterthrushes (Seiurus novaboracensis) in southwestern Puerto Rico during four nonbreeding seasons, 1996–1999. Densities were high (up to 13 birds/ha) on a 3-ha mature black mangrove (Avicennia germinans) study plot, but were significantly lower during periods of high water levels. Individuals exhibited site fidelity within and between seasons. Feeding areas were small (mean = 0.074 ha ± 0.041 SD) and there was considerable overlap tolerated among conspecifics. Waterthrush density decreased when water submerged their primary foraging substrate: woody debris and pneumatophores. Interannual returns were similar to other Neotropical migrants (mean = 50%) but site persistence was low due to periodic flooding. In September 1998, hurricane Georges flooded the plot and blew down >90% of the black mangrove trees. This drastic habitat alteration was followed by a drastic decline in waterthrushes using the study area. Individuals left feeding areas for overnight roost sites in red mangroves (Rhizophora mangle). This latter finding, coupled with site fidelity and high return rates concurrent with low site persistence, suggests that waterthrushes exhibit high plasticity in their use of habitat during the nonbreeding season, but may rely upon mangroves for overwinter survival.

We monitored the nesting biology of color-banded populations of the Louisiana Waterthrush (Seiurus motacilla) at up to 25 sites across Pennsylvania from 1996–2001. Opportunistic polygyny in this species was documented for the first time during our study. Four out of 283 paired males were polygynous; one male and female were involved in a polygynous trio during two successive years. Opportunistic polygyny may have occurred primarily as a result of female territory fidelity and a locally skewed sex ratio in two cases, but appeared to be actively pursued as a mating strategy in the case of the male who was bigamous during two successive years. His aggressive territorial behavior was consistent with that reported for polygynous birds having naturally and experimentally elevated plasma levels of testosterone. The rate of nestling provisioning by this male at a failed secondary nest was substantially lower compared to his successful primary nest and compared to mean provisioning rates for monogamous males. In addition to reduced male parental care, protraction of the renesting interval following nest failure was another possible component cost of polygyny observed for one of the mates of this male. In this instance, both costs were borne by the first mated female, who was relegated to secondary status after her initial nest was depredated.

We compared breeding ecology, density, and reproductive success of Roadside Hawks (Buteo magnirostris) in two Guatemalan study areas during 1993 and 1994. Primary forest supported 1.15 territorial pairs/km² whereas a slash-and-burn farming landscape supported 1.41 territorial pairs/km². All nests (n = 32) were in emergent trees. Hawks nested selectively in low canopy, seasonally inundated primary forest, and spacing of nests was related to the distribution of this forest type. Pairs did not nest selectively in a particular habitat in the farming landscape, but nested in isolated, emergent trees. Nest success (proportion of attempts that produced ≥1 fledgling) was 0.17 in the forested area and 0.30 in the farming landscape. Productivity (fledglings per territorial pair) was 0.08 in the forest and 0.32 in the farming landscape. Incidence of non-nesting by territorial pairs was greater in the forest (50%) than in the farming area (20%). The overall rate of nesting by territorial pairs was 65%. The most frequently identified cause of nest failure in the farming landscape was human persecution, while in the forest it was predation. Prey delivery rates did not differ significantly between habitats.

We tested whether Hooded Warblers (Wilsonia citrina) experienced a smaller food supply in small versus large forest fragments in northwestern Pennsylvania. Using 16 fragments that ranged in size from 0.7 to 214 ha, we videotaped parental feeding rates to nestlings in 35 nests and sampled arthropod abundance on 24 breeding territories. Contrary to our predictions, neither feeding rate per nestling nor arthropod abundance on breeding territories was significantly less in small (<4 ha) versus large (>150 ha) fragments. Brood loss due to starvation was rare and overall nest success was not significantly less in small fragments. Similarly, prey size delivered to nestlings and arthropod size sampled on territories did not differ significantly between fragment size classes. We conclude that Hooded Warblers breeding within small forest fragments in the northwest Pennsylvania landscape do not suffer from a relatively small food supply.

Bird species having specialized nesting substrates could suffer reduced reproductive success in habitats modified by human activities where optimal nest sites may be in short supply. We examined nest sites of Florida Scrub-Jays (Aphelocoma coerulescens) in intact, natural oak scrub and in scrub islands embedded in a suburban matrix. Despite differences in vegetation structure between natural and suburban scrubs, scrub-jays used scrub oaks (Quercus spp.) as substrate for >80% of all nests in both habitats. Because of fire suppression, vegetation in suburban scrubs tended to be taller than in natural scrubs; however, in both habitats jays appeared to prefer shrubs slightly taller than those available. In both habitats, nest height increased with nest shrub height, but the relationship was stronger in suburbs. In suburbs, the height of nests relative to nest shrub height remained constant, whereas in natural scrub, nest height declined relative to nest shrub height. In both habitats, nests built near the top of shrubs were associated with the presence of Smilax spp., a perennial vine that provides dense foliage near the crown of oak shrubs. However, 68% of all nests in suburbs were associated with Smilax, whereas in natural scrub 9% of nest sites had Smilax. Few nest site characteristics, including habitat, were associated with nest failure, but nests built in oak shrubs were more successful than nests built in other vegetation. Suburban nests built near the top of relatively tall shrubs appeared to be more vulnerable to wind damage.

We report an observation of egg predation by conspecifics in the Florida Scrub-Jay (Aphelocoma coerulescens) at Archbold Biological Station in Highlands County, Florida. This is the first confirmed account of intraspecific egg predation in this threatened and declining species. We observed a group of five jays harass an established breeding pair at their nest that contained four warm eggs. One female intruder alighted on the nest and carried off an egg in its beak. Other intruding females also were seen at the nest and presumably removed two more eggs. The following day, the nest was deserted and contained only one cold egg. We discuss potential reasons for such conspecific egg predation, focusing on resource limitation. We believe that further research in this area is essential for this species in which competition for resources (e.g., nesting habitat) intensifies as suitable habitat declines.

Nests, eggs, and chicks of nesting wading birds were unharmed by two fires in the Everglades. However, at least 50 adult White Ibises (Eudocimus albus) foraging away from the breeding colonies were killed during one fire. These results are counter-intuitive given that well-flighted adult birds seem more capable of escaping a fire than immobile nests or eggs. Nests probably were unharmed because of their location in wet willow (Salix carolina) and buttonbush (Cephalanthus occidentalis) islands. The adult birds foraging in a small cattail (Typha angustifolia) stand may have been trapped by flames in surrounding tall sawgrass (Cladium jamaicense) or debilitated by smoke inhalation. These observations provide insight into the direct effects of fire on wading bird breeding colonies and individual survival.

Reticuloendotheliosis (RE) is a viral disease documented from poultry, which has been found to cause mortality in captive Attwater's (Tympanuchus cupido attwateri) and Greater (T. c. pinnatus) prairie-chickens. We surveyed blood samples from 354 Greater Prairie-Chickens from seven states collected during 1998, 1999, and 2000, and from 184 Lesser Prairie-Chickens (T. pallidicinctus) from three states during 1999 and 2000, for the presence of RE virus proviral DNA using a polymerase chain reaction (PCR) test. All samples were negative for the presence of RE virus proviral DNA except for two samples collected from male Greater Prairie-Chickens taken in Oklahoma during 1998. This suggests that RE may not be a serious problem for most wild populations of prairie-chickens. Although our results were largely negative, because of the serious consequences of RE, the presence of the disease in wild populations of prairie-chickens should be carefully considered in any future relocation and reintroduction efforts.

Trichomoniasis, a digestive tract disease of raptors caused by ingesting the protozoan Trichomonas gallinae of infected columbid prey, recently was reported to be common in and an important agent of mortality among urban nestling and fledgling Cooper's Hawks (Accipiter cooperii) in Arizona. However, the prevalence of T. gallinae in wild raptor populations is poorly documented. During 2000 we detected T. gallinae in only three (2.7%) among 110 nestling Cooper's Hawks at 48 nests in both urban and rural habitats in Wisconsin, North Dakota, and British Columbia. Mortality attributable to trichomoniasis among 5- to 22-month-old Cooper's Hawks was zero in the three combined study areas. Prevalence of infection by T. gallinae seems to vary greatly among nesting Cooper's Hawks across this raptor's continental breeding range.