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Avian Conservation and Ecology
Journal Prestige (SJR): 0.684

Citation Impact (citeScore): 2
Number of Followers: 19

This is an Open Access Journal

Open Access journal
ISSN (Print) 1712-6568
Published by Society of Canadian Ornithologists

[1 journal]

Annual migratory movement, apparent molt-migration, migration schedule,
and diffuse migratory connectivity of Hermit Warblers
- Authors: Adrian Williams
  Abstract: Quantifying migratory connectivity and annual movement is key to sound conservation planning for migratory species. Hermit Warblers (Setophaga occidentalis) are an endemic-breeding species in the Pacific Northwest that winters in Mexico and the Central Americas. This species faces threats from mature forest loss and climate change throughout its range, but we know little about its migration ecology. To understand the annual movements and migratory connectivity of Hermit Warblers, we tracked 22 adult male Hermit Warblers from six breeding sites across the species’ breeding range using geolocators to examine migratory connectivity, spatiotemporal patterns, and migration routes. We found a high degree of mixing on the wintering grounds among birds from different breeding locations, indicating low migratory connectivity. However, birds breeding in Yosemite, the southernmost breeding location in our study, wintered farther east and south than birds from more northern breeding locations, providing weak evidence for potential chain migration. All birds showed much shorter and faster movements during spring migration than during fall migration. Birds arrived at breeding grounds from late April to mid-May and left breeding ranges from late June to mid-July. In fall, birds moved slowly from the breeding locations to montane regions in southern Oregon and California, which may indicate post-breeding molt before swiftly migrating to wintering grounds. Low migratory connectivity in this species implies that habitat and climate change across the broad wintering range may affect breeding populations throughout the species’ breeding range. A particularly compressed breeding schedule and departure of birds from the breeding grounds in early July may indicate that breeding is limited by a short window of favorable climatic conditions for breeding, which could signal heightened vulnerability under future climatic scenarios.The post Annual migratory movement, apparent molt-migration, migration schedule, and diffuse migratory connectivity of Hermit Warblers first appeared on Avian Conservation and Ecology.
  PubDate: Thu, 08 Aug 2024 18:28:28 +000
Weather and regional effects on winter counts of Rusty Blackbirds
(Euphagus carolinus)
- Authors: Adrian Williams
  Abstract: A long-term and severe population decline of Rusty Blackbirds (Euphagus carolinus) has motivated biologists to search for possible causes of the decline. Several hypotheses have been forwarded, one of which is that habitat destruction on the overwintering grounds is responsible. Climate change is another possible explanation. We evaluated the population trend of Rusty Blackbirds in Arkansas by modeling their abundance recorded during Christmas Bird Counts conducted between 1965 and 2020. We used generalized additive modeling to evaluate population trends and explored the influence of weather, effort, habitat, and region on those trends. We found that counts of Rusty Blackbirds have increased by about 40 birds in Arkansas between 1965 and 2020; most of the increase occurred after 1995. We also found that proportion of forest land in each count circle’s county was inversely related to counts of Rusty Blackbirds but that temperature was a more important variable. During warmer years, fewer Rusty Blackbirds were counted. Rusty Blackbird geographic distribution also changed by decade; that change accounted for about 15% of the deviance in counts of Rusty Blackbirds. Finally, we observed a relationship between temperature and distribution; Rusty Blackbirds tended to overwinter in the northern portions of the state during warm years and more southerly portions of the state during cold years. Our analytical approach will be useful to anyone evaluating geographic shifts in populations that might be associated with climate change.The post Weather and regional effects on winter counts of Rusty Blackbirds (Euphagus carolinus) first appeared on Avian Conservation and Ecology.
  PubDate: Thu, 08 Aug 2024 12:44:52 +000
Bias-corrected natal dispersal estimates fill information gaps for
White-headed Woodpecker conservation
- Authors: Adrian Williams
  Abstract: Although the White-headed Woodpecker (Dryobates albolarvatus) has been used as a management indicator species to guide forest management in the western U.S., basic information on the dispersal behavior of this species is currently unavailable. However, understanding dispersal can provide key information for management and conservation by revealing the mechanisms by which species colonize new areas and restored habitat. To address this information gap, we tracked the dispersal of juvenile White-headed Woodpeckers from their natal areas to their first spring home range in 2014–2018 and estimated dispersal distances using an interval-censored bias correction method with field observations and aerial telemetry surveys. We also compared habitat features between dispersal locations and spring home ranges. The median bias-corrected dispersal distance was 22.2 km in the fall (95% confidence interval [CI] = 16.4, 29.1 km), with 90% of woodpeckers dispersing>4.8 km (95% CI = 2.7, 8.3 km). The following spring, the median bias-corrected natal dispersal distance was 24.6 km (95% CI = 17.9, 32.3 km), while 10 individuals with full detection histories dispersed a median of 7.7 km to their first breeding locations (range 1.2–23.0 km). Our natal dispersal estimates for juvenile White-headed Woodpeckers were longer than those for most other woodpecker species studied to date. In addition, we found that woodpeckers settled in mid-elevation areas with greater variation in canopy cover compared to dispersal locations. There was no difference in ponderosa pine (Pinus ponderosa) basal area between dispersal tracks and spring home ranges. White-headed Woodpeckers are a species of conservation concern due to habitat loss in western North America, and active management in Washington state seeks to restore overstocked ponderosa pine forests to pre-settlement tree densities which could benefit this woodpecker. Our results inform conservation and forest management efforts by suggesting that dispersing juveniles have the capacity to travel long distances to colonize restored forests.The post Bias-corrected natal dispersal estimates fill information gaps for White-headed Woodpecker conservation first appeared on Avian Conservation and Ecology.
  PubDate: Fri, 26 Jul 2024 13:51:32 +000
Asynchronous movement patterns between breeding and stopover locations in
a long-distance migratory songbird
- Authors: Adrian Williams
  Abstract: The species-specific migratory patterns and strategies of many songbirds remain unknown or understudied, as research in animal ecology is biased toward the breeding period, with the fewest studies on the migratory period across taxa. Identifying large-scale spatiotemporal migratory patterns is challenging, as individuals within a species may vary in their migratory behavior and strategies. The Yellow Warbler (Setophaga petechia) is a Nearctic-Neotropical migrant that is relatively well studied during the breeding season, but its species-wide migratory patterns remain understudied. Our aim in studying Yellow Warbler movement ecology was to characterize temporal migration patterns during fall migration. We sought to determine the temporal migration pattern among breeding locations, as determined by the hydrogen stable isotope values in feather samples collected at disjunct (~2000 km) stopover sites in the Gulf of Maine (n = 50) and the Gulf of Mexico (n = 150). We used a similarity matrix to group individuals into a geographic cluster by breeding location, which was then used as the response variable in a modeling analysis. Our results provide evidence that Yellow Warblers exhibit an asynchronous, type 1 temporal migration pattern with southern breeding populations initiating migration prior to northern populations. Using hydrogen isotopes, we identified the temporal migration patterns between geographic clusters, representing an individual’s breeding location, and stopover sites along the Gulf of Maine and Gulf of Mexico, which fills a gap in understanding Yellow Warbler migration ecology.The post Asynchronous movement patterns between breeding and stopover locations in a long-distance migratory songbird first appeared on Avian Conservation and Ecology.
  PubDate: Wed, 24 Jul 2024 20:00:25 +000
Breeding habitat loss linked to declines in Rufous Hummingbirds
- Authors: Adrian Williams
  Abstract: Habitat loss is the primary driver of biodiversity decline worldwide, but it remains unknown how land-cover change and, in general, habitat loss impact many migratory species, such as the Rufous Hummingbird (Selasphorus rufus). Here, we gathered 5115 occurrence records for the Rufous Hummingbird from professional and citizen-science data sets and parameterized species distribution models with four bioclimatic variables and two Landsat satellite spectral reflectance bands. We calculated the population change and change in the potential distribution of the Rufous Hummingbird across its breeding range in the Pacific Northwest of North America over the last 36 yr (1985–2021). Back-casting habitat suitability predictions over time, we provide the first quantifications of breeding habitat change for the Rufous Hummingbird, which has exhibited precipitous declines over the past two decades. Furthermore, we evaluated links between modeled habitat suitability, population abundance, and trends with a route-level analysis of Breeding Bird Survey data. We found notable habitat loss occurring in Bird Conservation Regions along the Pacific coast where the species is most abundant (54% and 34% decreases in suitable habitat area), with habitat loss in coastal regions linked to population decline. In contrast, we detected habitat gains in regions along the interior, northeastern edges of the breeding range (160% and 85% increases in suitable habitat area). However, increasing suitability does not guarantee species colonization of new habitat. Our results indicate the need to further investigate drivers of habitat loss, such as intensive forestry and suppression of early seral habitat, along the Pacific coast. Our modeling approach can be applied to efficiently detect and quantify habitat loss over time for a variety of taxa.The post Breeding habitat loss linked to declines in Rufous Hummingbirds first appeared on Avian Conservation and Ecology.
  PubDate: Thu, 18 Jul 2024 16:11:37 +000
Modeling forest bird population trends at U.S. Army Garrison Pōhakuloa
Training Area, Hawaiʻi
- Authors: Adrian Williams
  Abstract: Hawaiian avifaunal communities have suffered irrevocable harm and significant threats remain for extant species. It is increasingly important to monitor and document bird density to improve our understanding of how remaining species respond to changing climate and emergent stressors. In this paper, we report annual densities (2003–2020) of two native and four non-native forest bird species in a region of Hawaiʻi Island lacking previous estimates. We estimated long-term population trends and short-term trajectories within a Bayesian framework. Our findings support previous studies that demonstrated the negative impact of ungulate browsing on forest bird habitat. We also note a detection of the Japanese Bush Warbler (Cettia diphone), a recently documented non-native species. The forest bird population trends presented here fill a regional gap and help extend the understanding of bird populations on Hawaiʻi Island.The post Modeling forest bird population trends at U.S. Army Garrison Pōhakuloa Training Area, Hawaiʻi first appeared on Avian Conservation and Ecology.
  PubDate: Tue, 09 Jul 2024 18:59:02 +000
Environmental relationships, decadal changes, and regional decline of
Eastern Whip-poor-will (Antrostomus vociferus) and Chuck-will’s-widow
(Antrostomus carolinensis)
- Authors: Adrian Williams
  Abstract: Nightjars are a family of nocturnal and aerial insectivorous birds that have experienced long-term declines driven primarily by loss of habitat and prey populations. In Illinois, structured survey efforts documented the presence of Eastern Whip-poor-will (Antrostomus vociferus) and Chuck-will’s-widow (Antrostomus carolinensis) over 30 years ago, but their current distribution in the state is not well known. We deployed autonomous recording units at 142 locations during May–July 2022 to resurvey a uniform sampling grid developed by the Illinois Breeding Bird Atlas during 1986–1991 surveys, with the objective of estimating the current distribution of the species within the state and understanding how their distribution has changed over 30 years. We used a bird call identification algorithm, BirdNet, to detect Nightjars in 4-hour recordings and then manually verified detections where species were reported. We used single-season, single-species occupancy models and a suite of remotely sensed, ecological variables to identify key drivers of their current distribution relating to landcover, forest patch configuration, and forest disturbances. BirdNet was highly accurate at detecting Nightjars and reduced the time spent manually annotating recordings. Eastern Whip-poor-will were positively associated with large core forests and proportion of pastureland within a sampling block. Additionally, Eastern Whip-poor-will were more likely to occupy areas that had experienced low to moderate disturbance in forests. Covariates used to model Chuck-will’s-widow occupancy explained little variation in detection or occupancy. However, examining non-significant trends suggest some similar relationships as documented with Eastern Whip-poor-will. Compared to the 1986–1991 surveys, Chuck-will’s-widow populations remained constant while Eastern Whip-poor-will declined although the spatial distribution of occurrences for both species changed. Our results provide updated knowledge of the current distributions of Nightjars in our region and highlight the need for further studies examining the drivers of distribution particularly in the case of Chuck-will’s-widow.The post Environmental relationships, decadal changes, and regional decline of Eastern Whip-poor-will (Antrostomus vociferus) and Chuck-will’s-widow (Antrostomus carolinensis) first appeared on Avian Conservation and Ecology.
  PubDate: Thu, 27 Jun 2024 13:29:16 +000
Using autonomous recording units for vocal individuality: insights from
Barred Owl identification
- Authors: Adrian Williams
  Abstract: Recent advances in acoustic recording equipment enable autonomous monitoring with extended spatial and temporal scales, which may allow for the censusing of species with individually distinct vocalizations, such as owls. We assessed the potential for identifying individual Barred Owls (Strix varia) through detections of their vocalizations using passive acoustic monitoring. We placed autonomous recording units throughout the John Prince Research Forest (54°27' N, 124°10' W, 700 m ASL) and surrounding area, in northern British Columbia, Canada, from February to April 2021. The study area was 357 km2 with a minimum of 2 km between the 66 recording stations. During this period, we collected 454 Barred Owl calls, specifically the two-phrase hoot, from 10 recording stations, which were of sufficient quality for spectrographic analysis. From each call, we measured 30 features: 12 temporal and 18 frequency features. Using forward stepwise discriminant function analysis, the model correctly categorized 83.2% of the calls to their true recording location based on a 5-fold cross validation. The model showed substantial agreement between the recording station that the call was classified to originate from, and where the call was actually recorded. The most important features of the calls that enabled discrimination were call length, interval between the 4th and the 5th note, interval between the 6th and 7th note, and duration of the 8th note. Our results suggest that passive acoustic monitoring can be used not only to detect presence/absence of species but also, where vocalizations have individually distinct features, for population censusing.The post Using autonomous recording units for vocal individuality: insights from Barred Owl identification first appeared on Avian Conservation and Ecology.
  PubDate: Tue, 25 Jun 2024 19:04:27 +000
Radio transmitters do not influence physiological traits of wintering
Grasshopper Sparrows (Ammodramus savannarum) in the Chihuahuan Desert of
Mexico
- Authors: Adrian Williams
  Abstract: Radio transmitters are a commonly used method that allows researchers to obtain valuable biological and ecological data from avian populations. However, transmitters might negatively affect survival due to the physiological cost of carrying a device. The negative fitness effects of transmitters are likely to vary interspecifically. Therefore, understanding responses to transmitters by birds can help minimize researcher impact and refine the vital rate estimates derived from these approaches. In this study, we investigated the potential negative impact of radio transmitters on two physiological parameters (heterophil-to-lymphocyte ratio and scaled mass index) on the Grasshopper Sparrow (Ammodramus savannarum) during the non-breeding season in northern Mexico. Specifically, we used two sampling approaches: repeated measures and independent samples. With repeated measures, most radio-tagged individuals maintained similar values in their scaled mass index across the winter, and showed a statically non-significant increase in this variable. In addition, at the population level (independent samples), we observed no significant difference in the use of transmitters, based on the two physiological parameters. Our results for the non-breeding season are consistent with previous studies where researchers have reported no effects of radio transmitters on physiological parameters. In summary, the study provides insights into the lack of a transmitter effect on chronic stress and body mass index in this species, conducted in a challenging environmental stage of the annual cycle and within a grassland priority conservation area.The post Radio transmitters do not influence physiological traits of wintering Grasshopper Sparrows (Ammodramus savannarum) in the Chihuahuan Desert of Mexico first appeared on Avian Conservation and Ecology.
  PubDate: Thu, 20 Jun 2024 14:29:19 +000
Time of day, water coverage, and pond type impact waterbird abundance in
aquaculture ponds in Taiwan
- Authors: Adrian Williams
  Abstract: The loss of coastal wetlands represents a grave threat to waterbirds, prompting the use of artificial wetlands, such as aquaculture ponds, as a means of conservation. Aquaculture ponds are common in coastal areas and provide production value and ecological function as waterbird habitats. Past studies have examined how different assemblages of waterbirds use different types of aquaculture ponds, particularly based on water depth or water coverage. However, most studies have only been conducted during the daytime. As some waterdbird species are known to also exhibit nocturnal foraging behavior, it is important to also examine their nocturnal use of aquaculture ponds. Most waterbird surveys were conducted during the daytime, limiting our understanding of their nocturnal habitat utilization. This study conducted diurnal and nocturnal surveys on shorebirds, waterfowl, and Black-crowned Night Heron (Nycticorax nycticorax) ten times in three types of aquaculture ponds situated in the Cigu District of Tainan, namely fish/shrimp, hard clam, and abandoned ponds between October 2021 and November 2022. The results showed no significant difference in shorebird density between day and night. However, shorebird density in fish/shrimp ponds was significantly higher than in abandoned ponds. Conversely, waterfowl density exhibits a significant increase in abandoned ponds compared to the other two pond types, irrespective of diurnal or nocturnal conditions. Furthermore, waterfowl density in abandoned ponds was significantly higher during daylight compared to the nocturnal period. In the daytime, the density of night herons was significantly higher in abandoned ponds than in the other two ponds. Nevertheless, during nighttime, fish/shrimp ponds exhibit the highest density of night herons, significantly surpassing that found in hard clam ponds. Notably, water coverage also influences the density of both shorebirds and waterfowl. The foraging frequency of waterfowl and night herons was greater during nocturnal hours, while shorebirds did not exhibit significant variations between day and night. Consequently, this study underscores the significance of considering both diurnal and nocturnal habitats in formulating strategies for waterbird conservation.The post Time of day, water coverage, and pond type impact waterbird abundance in aquaculture ponds in Taiwan first appeared on Avian Conservation and Ecology.
  PubDate: Wed, 19 Jun 2024 15:10:21 +000

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