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At least 811 records · Page 45Linked to original sources

USGS1995

Demography of birds in a neotropical forest: Effects of allometry, taxonomy, and ecology

Comparative demographic studies of terrestrial vertebrates have included few samples of species from tropical forests. We analyzed 9 yr of mark—recapture data and estimated demographic parameters for 25 species of birds inhabiting lowland forests in central Panama. These species were all songbirds (Order Passeriformes) ranging in mass from 7 to 57 g. Using Jolly—Seber stochastic models for open populations, we estimated annual survival rate, population size, and recruitment between sampling periods for each species. We then explored relationships between these parameters and attributes such as body size, phylogenetic affiliation, foraging guild, and social behavior. Larger birds had comparatively long life—spans and low recruitment, but body size was not associated with population size. After adjusting for effects of body size, we found no association between phylogenetic affiliation and any demographic trait. Ecological attributes, especially foraging guild, were more clearly associated with interspecific variation in all demographic traits. Ant—followers had comparatively long life—spans, but species that participate in flocks did not live longer than solitary species. The allometric associations we observed were consistent with those demonstrated in other studies of vertebrates; thus, these relationships appear to be robust. Our findings that ecological factors were more influential than phylogenetic affiliation contrasts with comparative studies of temperate—zone birds and suggests that the relative importance of environmental vs. historical factors varies geographically.

Ecology↗

USGS1985

Interspecific competition among Hawaiian forest birds

The object of this study was to determine whether interspecific competition modified local geographic distribution, after taking into account the effect of habitat structure. The tendencies for 14 passerine birds to have positive or negative associations were examined, using 7861 sample points in seven native forests on the islands of Hawaii, Maui, and Kauai. All birds were at least partly insectivorous and were fairly common in forested areas, although some fed chiefly on nectar or fruit. Species—pairs were classified as primary or secondary potential competitors based on general dietary similarity. To evaluate the association between species and to account for the effect of individual species habitat preferences, partial correlations were computed for each species—pair in a study area from the simple correlations between the species and 26 habitat variables plus two quadratic terms to represent nonlinearity. The partial correlations represented a short—term ("instantaneous") assessment of the strength of competitive interactions, and did not reflect the accumulation of competitive displacement through time. Of 170 partial correlations in the analysis, only 10 indicated significant negative association. The general pattern was of positive association (76 significantly positive partials), which probably resulted from flocking and from attraction of birds to areas of resource superabundance. Two species showed consistent patterns of negative partial correlations over several adjacent study areas, the Japanese White—eye/Iiwi in montane Hawaii, and the Japanese White—eye/Elepaio in windward Hawaii; both patterns could be reasonably attributed to direct competition. Species—pairs were grouped by the native or exotic status of the component species. Native/exotic pairs had a significantly greater proportion of negative partial correlations (37%) than either native/native pairs (8%) or exotic/exotic pairs (0%). This pattern was consistent across the seven study areas and appeared to reflect the occurrence of interspecific competition along a broad and diffuse ecological "front" between a co—evolved native avifauna and recently introduced exotic species. The role of competition in the pattern was corroborated by the significantly higher proportion of negative partial correlations among species—pairs of primary potential competitors than among those of secondary potential competitors. Our results suggested that °47% of the primary potential competitors among native/exotic species—pairs may experience at least small depressions in local population density due to competition. Although the negative correlations were for the most part small (average negative r = 0.06), one species could eventually replace another as spatial displacement accumulated through time. The Japanese White—eye appeared to have a principal role in native/exotic interactions, with 62% of the partial correlations between it and native primary potential competitor species being negative. Noteworthy implications were that (1) it was important to account for the habitat responses of individual species when studying the role of interspecific competition in modifying small—scale geographic distribution; (2) competition was frequently sporadic in its geographic occurrence and in the species affected, thus supporting Wiens' (1977) theory of competition; and (3) as a consequence, the role of interspecific competition in modifying distribution may be difficult to detect statistically with small data sets.

Hawaii↗

USGS1986

Cavity-nesting birds and the cavity-tree resource in plains cottonwood bottomlands

Densities of, and potential nesting substrates for, cavity-nesting birds were examined in a mature plains cottonwood ( Populus sargentii ) community in northeastern Colorado. Although snag (dead tree) densities were low (0.66/ha), the cavity-nesting guild included 7 species with densities ≤ 463 birds/100 ha. This finding suggests that cavity nesters are not limited by snag densities. Most (94.2%) of the nest substrate for cavity-nesting birds was provided by live trees with large, dead limbs (≥ 10 cm in diam). Both total dead limb length and the number of trees with dead limbs were highly correlated ( P < 0.001) with the number of cavities excavated. Large trees (>55 cm in diam at breast ht [dbh]) and dead limbs 15-30 cm in diameter were preferred for cavity excavation. Because snags were a minor component of potential nest substrate, snag management may not be a useful concept for cavity-nesting birds in cottonwood bottomlands, and snag retention aspects of habitat models would be relatively unimportant for this forest type. Live-tree management is recommended.

Journal of Wildlife Management↗

USGS1999

Scrub-successional bird community dynamics in young and mature longleaf pine-wiregrass savannahs

Public agencies are required to manage for threatened and endangered species and for biodiversity. However, at times, management for threatened and endangered species precludes consideration of other species. We investigated how managing for red-cockaded woodpeckers (Picoides borealis) and biodiversity at the Savannah River Site (SRS), South Carolina, affected communities of bird species that use early-successional scrub habitat (hereafter, scrub-successional species). Management for red-cockaded woodpeckers at the SRS involved both (1) manipulating mature longleaf pine (Pinus palustris)-wiregrass (Andropogon spp.) stands via canopy thinning, removal of midstory trees, and prescribed burning; and (2) even-aged timber harvesting. The former management practice encouraged red-cockaded woodpeckers to establish new colonies in previously unoccupied stands (hereafter, 'recruitment' stands). The latter management practice is used to remove off-site planted pines and replant with preferred longleaf pines. We conducted a constant-effort mist net study in recruitment and regenerating stands (stands clearcut and planted with longleaf pine) during the breeding seasons of 1995-96. We hypothesized that the scrub-successional bird community in recruitment stands would have greater species richness and higher survival and reproductive rates per species than in regenerating stands. However, recruitment stands always had fewer scrub-successional species (1995:36 species; 1996:31 species) than regenerating stands (1995:54 species; 1996:55 species), and all species that occurred in recruitment stands also occurred in regenerating stands. Species which commonly occurred in both recruitment and regenerating stands had similar adult:juvenile ratios (P > 0.15) and relative proportion of adults in breeding condition (P > 0.05). We detected no difference in survival rates of Bachman's sparrows (Aimophila aestivalis), indigo buntings (Passerina cyanea), and of 'combined' scrub-successional birds between stand types (P > 0.05). We found that even-aged forestry is an important management practice for maintaining and increasing avian biodiversity on public lands, as well as an acceptable management practice for red-cockaded woodpeckers.

Journal of Wildlife Management↗

USGS1990

Habitat relationships and nest site characteristics of cavity-nesting birds in cottonwood floodplains

We examined habitat relationships and nest site characteristics for 6 species of cavity-nesting birds--American kestrel ( Falco sparverius ), northern flicker ( Colaptes auratus ), red-headed woodpecker ( Melanerpes erythrocephalus ), black-capped chickadee ( Parus atricapillus ), house wren ( Troglodytes aedon ), and European starling ( Sturnus vulgaris )--in a mature plains cottonwood ( Populus sargentii ) bottomland along the South Platte River in northeastern Colorado in 1985 and 1986. We examined characteristics of cavities, nest trees, and the habitat surrounding nest trees. Density of large trees (>69 cm dbh), total length of dead limbs ≥10 cm diameter (TDLL), and cavity density were the most important habitat variables; dead limb length (DLL), dbh, and species were the most important tree variables; and cavity height, cavity entrance diameter, and substrate condition at the cavity (live vs. dead) were the most important cavity variables in segregating cavity nesters along habitat, tree, and cavity dimensions, respectively. Random sites differed most from cavity-nesting bird sites on the basis of dbh, DLL, limb tree density (trees with ≥1 m dead limbs ≥10 cm diameter), and cavity density. Habitats of red-headed woodpeckers and American kestrels were the most unique, differing most from random sites. Based on current trends in cottonwood demography, densities of cavity-nesting birds will probably decline gradually along the South Platte River, paralleling a decline in DLL, limb tree density, snag density, and the concurrent lack of cottonwood regeneration.

Journal of Wildlife Management↗

USGS1994

Mourning dove population trend estimates from Call-Count and North American Breeding Bird Surveys

The mourning dove ( Zenaida macrour a) Call-count Survey and the North American Breeding Bird Survey provide information on population trends of mourning doves throughout the continental United States. Because surveys are an integral part of the development of hunting regulations, a need exists to determine which survey provides precise information. We estimated population trends from 1966 to 1988 by state and dove management unit, and assessed the relative efficiency of each survey. Estimates of population trend differ ( P < 0.05) between surveys in 11 of 48 states; 9 of 11 states with divergent results occur in the Eastern Management Unit. Differences were probably a consequence of smaller sample sizes in the Callcount Survey. The Breeding Bird Survey generally provided trend estimates with smaller variances than did the Callcount Survey. Although the Callcount Survey probably provides more withinroute accuracy because of survey methods and timing, the Breeding Bird Survey has a larger sample size of survey routes and greater consistency of coverage in the Eastern Unit.

continental United States↗

USGS2001

Breeding bird response to juniper woodland expansion

In recent times, pinyon ( Pinus spp. )-juniper ( Juniperus spp. ) woodlands have expanded into large portions of the Southwest historically occupied by grassland vegetation. From 1997-1998, we studied responses of breeding birds to one-seed juniper ( J. monosperma ) woodland expansion at 2 grassland study areas in northern Arizona. We sampled breeding birds in 3 successional stages along a grassland-woodland gradient: un-invaded grassland, grassland undergoing early stages of juniper establishment, and developing woodland. Species composition varied greatly among successional stages and was most different between endpoints of the gradient. Ground-nesting grassland species predominated in uninvaded grassland but declined dramatically as tree density increased. Tree- and cavity-nesting species increased with tree density and were most abundant in developing woodland. Restoration of juniper-invaded grasslands will benefit grassland-obligate birds and other wildlife.

Journal of Range Management↗

USGS1951

Removal and repopulation of breeding birds in a spruce-fir forest community

IN 1949, while engaged in population studies of birds in northern Maine, the authors accumulated considerable information concerning population dynamics of birds inhabiting the Spruce-Fir forest community. This information was obtained in connection with investigations of the effective control by breeding birds of an infestation of the spruce budworm, Choristoneura fumiferana Clem.

The Auk↗

USGS2006

Avian influenza virus and free-ranging wild birds

Recent media and news reports and other information implicate wild birds in the spread of highly pathogenic avian influenza in Asia and Eastern Europe. Although there is little information concerning highly pathogenic avian influenza viruses in wild birds, scientists have amassed a large amount of data on low-pathogenicity avian influenza viruses during decades of research with wild birds. This knowledge can provide sound guidance to veterinarians, public health professionals, the general public, government agencies, and other entities with concerns about avian influenza.

Asia, Eastern Europe↗

USGS2003

Effects of management practices on grassland birds: Greater Prairie-Chicken

Information on the habitat requirements and effects of habitat management on grassland birds were summarized from information in more than 5,500 published and unpublished papers. A range map is provided to indicate the breeding distribution of Greater Prairie-Chicken in the United States and southern Canada. Although birds frequently are observed outside the breeding range indicated, the maps are intended to show areas where managers might concentrate their attention. It may be ineffectual to manage habitat at a site for a species that rarely occurs in an area. The species account begins with a brief capsule statement, which provides the fundamental components or keys to management for the species. A section on breeding range outlines the current breeding distribution of the species in North America. The suitable habitat section describes the breeding habitat and occasionally microhabitat characteristics of the species, especially those habitats that occur in the Great Plains. Details on habitat and microhabitat requirements often provide clues to how a species will respond to a particular management practice. A table near the end of the account complements the section on suitable habitat, and lists the specific habitat characteristics for the species by individual studies. A special section on prey habitat is included for those predatory species that have more specific prey requirements. The area requirements section provides details on territory and home range sizes, minimum area requirements, and the effects of patch size, edges, and other landscape and habitat features on abundance and productivity. It may be futile to manage a small block of suitable habitat for a species that has minimum area requirements that are larger than the area being managed. The section on breeding-season phenology and site fidelity includes details on spring arrival and fall departure for migratory populations in the Great Plains, peak breeding periods, the tendency to renest after nest failure or success, and the propensity to return to a previous breeding site. The duration and timing of breeding varies among regions and years. Species’ response to management summarizes the current knowledge and major findings in the literature on the effects of different management practices on the species. The section on management recommendations complements the previous section and summarizes specific recommendations for habitat management provided in the literature. If management recommendations differ in different portions of the species’ breeding range, recommendations are given separately by region. The literature cited contains references to published and unpublished literature on the management effects and habitat requirements of the species. This section is not meant to be a complete bibliography; a searchable, annotated bibliography of published and unpublished papers dealing with habitat needs of grassland birds and their responses to habitat management is posted at the Web site mentioned below.

Kansas, Oklahoma, Colorado, Missouri, Illinois, Wi↗

USGS2004

Effects of management practices on grassland birds: Greater Sage-Grouse

Information on the habitat requirements and effects of habitat management on Greater Sage-Grouse was summarized from information in more than 5,500 published and unpublished papers. A range map is provided to indicate the current range of Greater Sage-Grouse (adapted from Schroeder et al. 2004). Although birds may be observed outside the breeding range indicated, the maps are intended to show areas where managers might concentrate their attention. It may be ineffectual to manage habitat at a site for a species that rarely occurs in an area. The species account begins with a brief capsule statement, which provides the fundamental components or keys to management for the species. A section on breeding range outlines the current breeding distribution of the species in North America. The suitable habitat section describes the breeding habitat and occasionally microhabitat characteristics of the species. Details on habitat and microhabitat requirements often provide clues to how a species will respond to a particular management practice. A table near the end of the account complements the section on suitable habitat, and lists the specific habitat characteristics for the species by individual studies. A special section on prey habitat is included for those predatory species that have more specific prey requirements. The area requirements section provides details on territory and home range sizes, minimum area requirements, and the effects of patch size, edges, and other landscape and habitat features on abundance and productivity. It may be futile to manage a small block of suitable habitat for a species that has minimum area requirements that are larger than the area being managed. The Brown-headed Cowbird ( Molothrus ater ) is an obligate brood parasite of many grassland birds. The section on cowbird brood parasitism summarizes rates of cowbird parasitism, host responses to parasitism, and factors that influence parasitism, such as nest concealment and host density. The impact of management depends, in part, upon a species’ nesting phenology and biology. The section on breeding-season phenology and site fidelity includes details on spring arrival and fall departure for migratory populations, peak breeding periods, the tendency to renest after nest failure or success, and the propensity to return to a previous breeding site. The duration and timing of breeding varies among regions and years. Species’ response to management summarizes the current knowledge and major findings in the literature on the effects of different management practices on the species. The section on management recommendations complements the previous section and summarizes specific recommendations for habitat management provided in the literature. If management recommendations differ in different portions of the species’ breeding range, recommendations are given separately by region. The literature cited contains references to published and unpublished literature on the management effects and habitat requirements of the species. This section is not meant to be a complete bibliography; a searchable, annotated bibliography of published and unpublished papers dealing with habitat needs of shrub-steppe birds and their responses to habitat management is posted at the Web site mentioned below.

Oregon, Washington, California, Nevada, Idaho, Mon↗

USGS2004

Effects of management practices on grassland birds: Prairie Falcon

Information on the habitat requirements and effects of habitat management on grassland birds were summarized from information in more than 4,000 published and unpublished papers. A range map is provided to indicate the breeding, year-round, and nonbreeding ranges in the United States and southern Canada. Although birds frequently are observed outside the breeding range indicated, the maps are intended to show areas where managers might concentrate their attention. It may be ineffectual to manage habitat at a site for a species that rarely occurs in an area. The species account begins with a brief capsule statement, which provides the fundamental components or keys to management for the species. A section on breeding range outlines the current breeding distribution of the species in North America. The suitable habitat section describes the breeding habitat and occasionally microhabitat characteristics of the species, especially those habitats that occur in the Great Plains. Details on habitat and microhabitat requirements often provide clues to how a species will respond to a particular management practice. A table near the end of the account complements the section on suitable habitat, and lists the specific habitat characteristics for the species by individual studies. A special section on prey habitat is included for those predatory species that have more specific prey requirements. The area requirements section provides details on territory and home range sizes, minimum area requirements, and the effects of patch size, edges, and other landscape and habitat features on abundance and productivity. It may be futile to manage a small block of suitable habitat for a species that has minimum area requirements that are larger than the area being managed. The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite of many grassland birds. The section on cowbird brood parasitism summarizes rates of cowbird parasitism, host responses to parasitism, and factors that influence parasitism, such as nest concealment and host density. The impact of management depends, in part, upon a species' nesting phenology and biology. The section on breeding-season phenology and site fidelity includes details on spring arrival and fall departure for migratory populations in the Great Plains, peak breeding periods, the tendency to renest after nest failure or success, and the propensity to return to a previous breeding site. The duration and timing of breeding varies among regions and years. Species’ response to management summarizes the current knowledge and major findings in the literature on the effects of different management practices on the species. The section on management recommendations complements the previous section and summarizes specific recommendations for habitat management provided in the literature. If management recommendations differ in different portions of the species' breeding range, recommendations are given separately by region.

Report↗

USGS2005

Using radar to advance migratory bird management: An interagency collaboration

Migratory birds face many changes to the landscapes they traverse and the habitats they use. Wind turbines and communications towers, which pose hazards to birds and bats in flight, are being erected across the United States and offshore. Human activities can also destroy or threaten habitats critical to birds during migratory passage, and climate change appears to be altering migratory patterns. The U.S. Fish and Wildlife Service (USFWS) and other agencies are under increasing pressure to identify and evaluate movement patterns and habitats used during migration and other times.

Fact Sheet↗

USGS2005

Migratory bird pathways and the Gulf of Mexico: Importance of Louisiana's coast

Because of its geographic position, Louisiana plays an important role in the hemispheric-scale phenomenon known as the Nearctic-Neotropical bird migration system. Each year millions of landbirds migrate across or near to the coast of the Gulf of Mexico. Birds migrate in large, broad fronts that sometimes exceed 2 million individuals, and there is an advantage for them to take a direct north-south route (the shortest distance). During migration seasons, nearly all of the migratory landbird species of the eastern United States, as well as many western species, use the coastal plains of the western gulf. Spring migrants arrive with depleted energy reserves and depend on Louisiana's coastal habitats to provide food and cover after long gulf crossings. Fall migrants depend on Louisiana’s coastal habitats for food to store fat reserves just prior to gulf crossings in autumn. Mortality during the migratory period can be high. Recent research on the black-throated blue warbler ( Dendroica caerulescens ) indicates that more than 85% of the annual mortality for the species occurs during migration. Migrants en route tend to concentrate in habitats adjacent to ecological barriers; DOI land managers need to identify key coastal landscape features that are important to these birds. Because of the vastness of the North American continent, it is nearly impossible to delineate movement patterns and migration pathways by using traditional ground-based surveys.

Fact Sheet↗

USGS2009

Surveillance plan for the early detection of H5N1 highly pathogenic avian influenza virus in migratory birds in the United States: surveillance year 2009

Executive Summary: This Surveillance Plan (Plan) describes plans for conducting surveillance of wild birds in the United States and its Territories and Freely-Associated States to provide for early detection of the introduction of the H5N1 Highly Pathogenic Avian Influenza (HPAI) subtype of the influenza A virus by migratory birds during the 2009 surveillance year, spanning the period of April 1, 2009 - March 31, 2010. The Plan represents a continuation of surveillance efforts begun in 2006 under the Interagency Strategic Plan for the Early Detection of H5N1 Highly Pathogenic Avian Influenza in Wild Migratory Birds (U.S. Department of Agriculture and U.S. Department of the Interior, 2006). The Plan sets forth sampling plans by: region, target species or species groups to be sampled, locations of sampling, sample sizes, and sampling approaches and methods. This Plan will be reviewed annually and modified as appropriate for subsequent surveillance years based on evaluation of information from previous years of surveillance, changing patterns and threats of H5N1 HPAI, and changes in funding availability for avian influenza surveillance. Specific sampling strategies will be developed accordingly within each of six regions, defined here as Alaska, Hawaiian/Pacific Islands, Lower Pacific Flyway (Washington, Oregon, California, Idaho, Nevada, Arizona), Central Flyway, Mississippi Flyway, and Atlantic Flyway.

General Information Product↗

USGS2010

Preliminary use of uric acid as a biomarker for wading birds on Everglades Tree Islands, Florida, United States

Concentrations of organic biomarkers and concentrations of phosphorus in soil cores can potentially be used as proxies for historic population densities of wading birds on tree islands in the Florida Everglades. This report focuses on establishing a link between the organic biomarker uric acid found in wading bird guano and the high phosphorus concentrations in tree island soils in the Florida Everglades. Uric acid was determined in soil core sections, in surface samples, and in bird guano by using a method of high-performance liquid chromatography-mass spectrometry (HPLC-MS) developed for this purpose. Preliminary results show an overall correlation between uric acid and total phosphorus in three soil cores, with a general trend of decreasing concentrations of both uric acid and phosphorus with depth. However, we have also found no uric acid in a soil core having high concentrations of phosphorus. We believe that this result may be explained by different geochemical circumstances at that site.

Florida↗

USGS2015

Estimating exposure of piscivorous birds and sport fish to mercury in California lakes using prey fish monitoring: a predictive tool for managers

Numerous water bodies in California are listed under the Clean Water Act as being impaired due to mercury (Hg) contamination. The Surface Water Ambient Monitoring Program (SWAMP), via the Bioaccumulation Oversight Group (BOG), has recently completed statewide surveys of contaminants in sport fish tissue from more than 250 lakes and rivers in California and throughout coastal waters. This effort focused on human health issues but did not include beneficial uses by wildlife. Many piscivorous birds such as grebes, terns, cormorants, and mergansers eat fish smaller than those that were sampled by BOG, and sport fish Hg concentrations are not always indicative of wildlife exposure to Hg; therefore, the BOG surveys could not address whether wildlife were at risk due to Hg-induced reproductive impairment in these lakes. We used western grebes ( Aechmophorus occidentalis ) and Clark’s grebes ( Aechmophorus clarkii ) as our index of wildlife exposure to Hg in California lakes. Grebes are widely distributed in lakes throughout California and, as piscivorous waterbirds, are near the top of the food chain in lakes. Additionally, grebes become flightless after they arrive at their summer locations. Thus, grebes are useful representatives for wildlife risk from local, lake-specific contaminant exposure. Grebes also breed at many lakes throughout California, making them susceptible to impaired reproduction due to local Hg contamination. We developed a tool for estimating wildlife and sport fish risk from Hg exposure based on Hg concentrations in prey fish. This quantitative tool can be used to predict Hg concentrations in grebe blood, grebe eggs, and sport fish, thus facilitating a feasible alternative for adequately estimating wildlife exposure when more comprehensive wildlife sampling is not possible. Specifically, we sampled grebes, prey fish, and sport fish simultaneously at 25 lakes throughout California during the spring and summer of 2012 and 2013 when breeding birds are particularly vulnerable to Hg-induced reproductive impairment. We selected lakes based on a combination of factors, including lakes from southern and northern California, of various sizes, shapes, and elevations, with a range of sport fish Hg exposure levels , where largemouth bass ( Micropterus salmoides ) was the primary sport fish, and with a history of use by grebes. Using these factors ensured that our results are representative of a broad range of lakes and reservoirs in California and are comparable to prior BOG studies. Specifically, we addressed three management questions: Does methylmercury pose significant risks to aquatic life in a representative sample of California lakes and reservoirs? Can a correlational approach be applied on a statewide basis to estimate risks to birds? What are appropriate water-quality monitoring requirements to address methylmercury exposure in wildlife?

California↗

USGS2024

Neotropical migratory bird monitoring study at Marine Corps Base Camp Pendleton, California—2021 annual data summary

Executive Summary Two Monitoring Avian Productivity and Survivorship (MAPS) stations were operated at Marine Corps Base Camp Pendleton (MCBCP), California, in 2021: one at De Luz Creek and one at the Santa Margarita River. The stations were established to provide data on Neotropical migratory birds at MCBCP to support the dual missions of environmental stewardship and military readiness. A total of 1,227 individual birds were captured in 2021 between the two stations: 395 at De Luz and 832 at Santa Margarita (both 15 banding days). Of these 1,227 individuals captured, 955 were newly banded (273 at De Luz and 682 at Santa Margarita), 150 were recaptures banded before 2021 (28 at De Luz and 122 at Santa Margarita, excluding recaptures released before reading band number [1 at De Luz and 3 at Santa Margarita]), and 118 were unbanded (93 at De Luz and 25 at Santa Margarita). Return rate in 2021 was much lower than the annual mean at De Luz (1995–2019) and similar to the annual mean at the Santa Margarita station (1998–2020). The sex ratio of known-sex adult birds was skewed toward males at both stations in 2021. Species richness was similar at De Luz from 2019 to 2021, increased at Santa Margarita from 2020 to 2021 and was above annual means at both sites (1995–2019 and 1998–2020, respectively). The most abundant species at De Luz were Wrentit ( Chamaea fasciata ) and Allen’s Hummingbird ( Selasphorus sasin ). Song Sparrow ( Melospiza melodia ) and Common Yellowthroat ( Geothlypis trichas ) were most abundant at Santa Margarita. Since 2002, we have examined the population trends of 12 species at De Luz and 13 species at Santa Margarita for which numbers of known-age individuals were adequate for statistical analysis. We estimated population size and calculated indices of productivity and survival for a subset of these species with sufficient captures and recaptures for valid parameter estimation—four at De Luz and six at Santa Margarita. We determined that in 2021, abundance of 42 percent (5 of 12) of focal species at De Luz and 38 percent (5 of 13) of focal species at Santa Margarita was below the annual mean abundance. Of the focal species below mean abundance, 40 percent (2 of 5) at De Luz and 60 percent (3 of 5) at Santa Margarita were migrant populations. Of the focal species, 25 (3 of 12) percent at De Luz and 31 percent (4 of 13) at Santa Margarita had declining population trends during the span of station operation. With few exceptions, these declines appeared to be associated with conditions on the breeding grounds. Annual productivity (calculated as the ratio of juveniles to adults among individual captures) was zero for all focal species at De Luz in 2021. At Santa Margarita, productivity increased from year 2020 to 2021 for Common Yellowthroat, Song Sparrow, and Yellow Warbler ( Setophaga petechia ) and declined from year 2020 to 2021 for Least Bell’s Vireo ( Vireo bellii pusillus ), but productivity was above the 1998–2020 mean for all four species, whereas productivity was maintained for Orange-crowned Warbler ( Leiothlypis celata ) and Yellow-breasted Chat ( Icteria virens ). Winter precipitation affected productivity of Black-headed Grosbeak ( Pheucticus melanocephalus ), Common Yellowthroat, and Song Sparrow at De Luz and affected productivity of Common Yellowthroat, Orange-crowned Warbler, Song Sparrow, Yellow-breasted Chat, and Yellow Warbler at Santa Margarita. We calculated the mean annual adult survival for 1998–2020 at Santa Margarita, excluding years when the station was not operated. Survival could not be calculated for De Luz in 2021 because the station was not operated in 2020. Model-averaged annual adult survival ranged from 42 to 66 percent for residents and from 30 to 66 percent for migrants at Santa Margarita. Survival of Common Yellowthroat, Song Sparrow, and possibly Yellow Warbler was found to be affected by winter precipitation. Sex was a significant predictor of survival for Common Yellowthroat, Least Bell’s Vireo, Orange-crowned Warbler, and Yellow-breasted Chat at Santa Margarita, where females were found to have lower survival than males. At Santa Margarita, multiple regression analyses examining adult survival and productivity as predictors of future population size indicated that resident Song Sparrow and migrant Yellow Warbler populations were affected by population size from the previous year, migrant Yellow-breasted Chat populations were affected by productivity from the previous year, and migrant Orange-Crowned Warbler populations were affected by survival from the previous year. Updated previous-year population size predictions could not be calculated for De Luz because the station was not operated in 2020.

California↗