To evaluate the status of Florida's threatened Crested Caracara (Caracara cheriway) population, knowledge of life history parameters and population dynamics is required. Using the program MARK, I estimated survival rates for adult and juvenile Crested Caracaras from breeding areas in southcentral Florida during the period February 1994 through March 2000. Annual adult survival probabilities estimated from resightings of banded individuals and derived using model averaging were 0.876 for males and 0.906 for females. Results of modeling monthly juvenile caracara survival from radiotelemetry data identified differences in survival for two age groups: juveniles (up to age 3 years) and adults (age >3 years). Using this age-effects model, monthly survival for juvenile caracaras was estimated to be 0.970, indicating an annual survival rate of 0.694 and an overall probability of 0.334 of an individual surviving to age 3, when it could potentially become a breeder. Juvenile caracaras experienced periods of decreased survivorship beginning at two months after fledging, which coincides with the fledglings' independence, and about one year after fledging, when juveniles typically leave their natal breeding area. Along with protecting suitable nesting habitat to enhance survival and breeding of adults, conservation and management strategies for Florida's caracaras should focus on identifying and protecting areas where groups of individuals in the juvenile age class congregate. Such protection would enhance survival of these individuals, thus ensuring their continued recruitment into the breeding population.

Little is known about the life history and reproduction of the Curl-crested Jay (Cyanocorax cristatellus), despite its conspicuousness and endemic status, being restricted primarily to the central Cerrado biome of Brazil. From May 1999 to December 2000, we examined the sizes of home ranges and foraging and reproductive patterns in this species. Average group size was approximately 10 individuals, with average home ranges of 172 ha; during the reproductive period individuals in the group tended to stay within approximately 29 ha of active nests. These jays are dietary generalists, while the diversity of substrates and capture techniques employed showed high flexibility in resource utilization. The reproductive period was from September to March, and groups produced average clutch sizes of 5.7 eggs, but only 35% of these hatched and only 25% of the nests produced at least one fledgling. Predation was the chief cause of nesting failure, accounting for 63% of nest loss. The occurrence of large groups year-round with several individuals providing parental care and evidence of just one female laying eggs suggest that the Curl-crested Jay is a cooperative breeder with a high degree of sociality. However, further study is necessary to exclude the possibility that more than one female is laying eggs in a single nest.

We studied the breeding biology, site fidelity, and dispersal of Grasshopper Sparrows (Ammodramus savannarum) from 1996 to 2000 in a fragmented landscape in western New York State. Ten fields (1.8–13.2 ha) contained territorial male Grasshopper Sparrows during the study; total territorial males in the study area varied between 31 and 19 birds. In 1996, eight fields were occupied; five extinctions and two colonizations occurred between 1997–2000. Fields that suffered extinctions were smaller than fields in which subpopulations persisted or colonizations occurred. Adult return rates (0.33 vs. 0.16), nest success (0.59 vs. 0.25) and average number of fledglings/female/year (2.3 vs. 1.3) tended to be higher in fields ≥8 ha. Estimates of λ, the finite rate of increase, were 0.23 for small fields and 0.46 for large fields. Although sample sizes were small, our data suggest that return rates and productivity were greater in large than in small habitat patches. However, even the larger habitat patches in our study area appeared to function as population sinks, suggesting that the Grasshopper Sparrow population is unlikely to persist without immigration. Survival prospects for our study population are poor, given its demographic characteristics and the fragmented nature and continuing loss of grassland habitat. Our results suggest that conservation efforts in the Northeast should focus on protecting large patches of continuous grassland habitat.

We investigated the effect of time of season on the accuracy of species number estimation from point-count data collected at 28 oases from southern Tunisia. Each oasis was visited at the beginning of the breeding season and two months later, which allowed us to conduct counts on five points per oasis per visit. For each oasis, we considered the observed species number as the total number of species recorded during each visit, and we used a capture-recapture approach to estimate species number from patterns of presence and absence of species over the five points. We found that birds were more detectable at the beginning of the breeding season than two months later, and the observed species number showed a significant decrease between the two periods. However, when a capture-recapture approach accounting for heterogeneity in species detectability was used, similar estimates were obtained from data collected during both periods. Nonetheless, the estimates obtained at the beginning of the breeding season were more precise than those obtained later. Overall, our results illustrate once more the need of taking into account time of season as an important source of bias when attempting to determine species richness from count data, and stress the need for using probabilistic approaches in such an investigation.

Subspecies of Canada Geese (Branta canadensis) exhibit wide variation in body size across their range. To monitor harvest levels in the Pacific Flyway, biologists commonly use culmen length and plumage color to differentiate among subspecies on sympatric wintering grounds. Among the four large-bodied Pacific subspecies (B. c. parvipes, B. c. occidentalis, B. c. fulva, and B. c. moffitti), overlap in culmen length and subjectivity of visually assessing color results in misclassification and inaccurate harvest estimates. We examined the morphology of Pacific large-bodied Canada Geese to characterize body size variation among subspecies and provide more discriminatory measures for harvest assessments. We found that culmen length, one of the most commonly used field measures, overlapped widely among subspecies, and it had little support for inclusion in discriminatory models. Morphological measures with greater explanatory power included bill width at nail, bill width at base, head length, and mid wing. If culmen length and plumage color continue to be used to assess winter harvest, we recommend the addition of at least one sex-specific measurement to reduce levels of misclassification among subspecies. If an additional morphological measure is included, further evaluation on the wintering grounds should be conducted as this measure's effectiveness may vary depending upon observer bias, temporal and spatial variation in subspecies abundance, and the proportion of birds accurately sexed by cloacal examination.

Male and female Rock Shags (Phalacrocorax magellanicus) are not obviously sexually dimorphic in plumage or size and are thus difficult to distinguish in the field. We evaluated the utility of two different DNA-based techniques for sexing adult Rock Shags. We found that the primer set 2550F/2718R (originally tested in three individuals of P. carbo), with minor differences in the forward primer, provided a consistent and simple sexing method for Rock Shags. Moreover, we obtained three reliable discriminant functions for sexing adults from three different colony sites between 42° to 47°S in coastal Patagonia, Argentina. Discriminant analysis of five external characters of adult birds indicated that head, bill, and wing lengths were the most accurate variables for use in a discriminant function model, predicting the sex of 80–86% of the birds. Males were significantly larger than females for all body measurements except for bill depth. Rock Shags showed less marked sexual dimorphism than other phalacrocoraciid species.

Line transects based on distance sampling methodology were used to census nocturnal raptor species in three different primary lowland forest habitats in the Tambopata region, southeastren Peru. Density estimates were calculated for five owl species in these forest habitats. In general, species were more abundant in primary old floodplain or primary middle/upper floodplain forests than in primary seasonally flooded swamp forest. Density estimates were also higher than those calculated from traditional spot-mapping methods in other lowland forest sites in southeastern Peru and French Guiana. There was no significant difference in the number of individual owls recorded during nights with different cloud cover or during different phases of the moon. Problems of distance estimation at night and unfamiliarity with a range of vocalizations, particularly with Strix owls, may be overcome by conducting a practice period before surveys are undertaken, with transect routes and distance markers adequately set out. Walking transect routes during daylight hours in a practice period also helps to overcome concerns of observer safety.

Offshore censuses of birds are lacking for inland seas, such as the Laurentian Great Lakes, but may provide valuable information for managing species that are in conflict with human interests. Birds were counted along 31 established transects in four habitats in western Lake Erie: offshore of waterbird refuges, offshore of beaches with human development, on reefs and shoals, and in open water. A total of 161 10-min counts were conducted between 24 April and 1 September 2000. The mean number of aquatic bird species/km² (species density) was greater offshore of refuges than on open water. For all habitats combined, species density increased over time. This was mainly due to the arrival of Bonaparte's Gulls (Larus philadelphia) and Great Black-backed Gulls (L. marinus), two fall and winter residents that do not breed in the study area, and increased use of open water and reefs and shoals by Herring Gulls (L. argentatus) and Ring-billed Gulls (L. delawarensis) after the nesting season. Species density was not strongly spatially autocorrelated, either for all species or for only those species that were floating on the water when recorded. Neither Double-crested Cormorants (Phalacrocorax auritus) nor Herring Gulls exhibited spatial autocorrelation. In contrast, Bonaparte's and Ring-billed gulls exhibited positive spatial autocorrelations. Unlike marine studies, species density was only weakly associated with water depth. This result was due mainly to Double-crested Cormorants, the only diving bird species that lived year-round in the area, which preferred reefs and shoals (depth 3–6 m) over open water (≥10 m). The results suggest that offshore habitat influences species density in this area during the breeding and immediate post-breeding seasons.

The use of nest boxes by Vaux's Swifts (Chaetura vauxi) was investigated because of the loss of large-diameter hollow trees used for nesting in northwestern North America. Nest attempts and nest success were compared in nest boxes among three habitat types in northeastern Oregon. Air temperatures in the boxes were monitored to determine if boxes overheated and resulted in nestling mortality. Thirty of 103 nest boxes were used by nesting Vaux's Swifts for at least one year during 1999–2002. Of 51 nest attempts, 53% successfully fledged 1–6 young (x̄ = 3.5 nestlings). Over this 4-yr period, 47% of the nests were in late-seral stage grand fir (Abies grandis) stands, 31% were in harvested stands of grand fir, and 22% were in ponderosa pine (Pinus ponderosa) stands. It appeared that temperature did not affect nest success in boxes because there were no significant differences in maximum and minimum temperatures between successful and unsuccessful nest attempts. Nest boxes provided alternative nest sites for Vaux's Swifts in habitats traditionally used by this species as well as in habitats that currently lack natural nest sites.

Development of effective trapping techniques is important for conservation efforts, as marking and subsequent monitoring of individuals is necessary to obtain accurate estimates of demography, movements, and habitat use. We describe a leg-hold noose-mat trap for capturing breeding and nonbreeding shorebirds. Using this method, we trapped 50 Piping Plovers (Charadrius melodus), 2258 Snowy Plovers (C. alexandrinus), 38 Killdeers (C. vociferus), and 64 Dunlins (Calidris alpina) in the western and southern United States. The trap was lightweight, making it easy to transport and set up. It was effective on unvegetated substrates at both coastal and inland sites and could be modified for a variety of habitats. Furthermore, this trap allowed researchers to target specific groups of birds including territorial individuals. Easy removal of birds from traps minimized handling time, stress, and injury.

The ‘Elepaio (Chasiempis sandwichensis) is a monarch flycatcher endemic to the Hawaiian Islands. Both sexes have a two-year delay in plumage maturation, with distinct first-year and second-year subadult plumages. This study tested hypotheses for the evolution of delayed plumage maturation in ‘Elepaio by presenting adult males with models representing different ages and sexes in the breeding and nonbreeding seasons. The subadult plumages of ‘Elepaio appeared to serve as honest, graded signals of status that reduced aggression from dominant adults. Both first-year and second-year subadult male models were attacked less than adult male models, and aggression increased linearly with age of male models. Neither subadult plumage appeared to function in sexual mimicry or juvenile mimicry. Second-year male models were attacked more than adult female models; neither subadult plumage resembles adult plumage of the opposite sex. First-year male models, which are juvenile-like, were not attacked more than adult female models, but juvenile mimicry cannot account for the behavior toward second-year male models and is a less parsimonious explanation. Aggression toward models was much higher in the breeding season, and all models were treated similarly in the nonbreeding season, suggesting competition for mates has been the primary selective force shaping the evolution of the ‘Elepaio's plumage coloration. Models made from color photocopies can be a useful alternative to museum specimens in behavioral studies of rare species or those in which damage to specimens during model presentation would occur.

We used solar-powered time-lapse video photography to document nesting Gyrfalcon (Falco rusticolus) food habits in central West Greenland from May to July in 2000 and 2001. We collected 2677.25 h of videotape from three nests, representing 94, 87, and 49% of the nestling period at each nest. The video recorded 921 deliveries of 832 prey items. We placed 95% of the items into prey categories. The image quality was good but did not reveal enough detail to identify most passerines to species. We found no evidence that Gyrfalcons were negatively affected by the video system after the initial camera set-up. The video system experienced some mechanical problems but proved reliable. The system likely can be used to effectively document the food habits and nesting behavior of other birds, especially those delivering large prey to a nest or other frequently used site.

Date of clutch initiation and mean clutch size for an alpine population of American Pipits (Anthus rubescens) in northern Wyoming varied significantly among seven years sampled during 1963–1995. Because American Pipits are obligate ground-nesters in an environment devoid of trees, I examined the hypothesis that spring snow conditions cause the annual variation in mean laying date and resulting clutch size. Mean clutch size was highly correlated with mean laying date, and both traits were highly correlated with the snow water equivalent (SWE) on 1 May. Reduced SWE resulted in earlier onset of egg laying and indirectly in increased clutch size. Trend analyses for 1961–2002 showed an 18% decline in 1 May SWE and an earlier date of snowmelt by 7 d, indicating that an earlier onset of egg laying by about 5 d may have occurred over the same period, with a corresponding increase in mean clutch size of 0.2 eggs. This result supports the global pattern for various bird species of earlier onset of nesting during the last few decades. Annual laying date and clutch size of American Pipits appear to respond predictably to short-term (annual) changes in spring snow conditions at this high-elevation location and may prove useful for projecting reproductive responses of alpine birds to changing trends in climate.