Breeding habitat loss linked to declines in Rufous Hummingbirds

BackgroundHabitat loss can force animals to relocate to new areas, where they would need to adjust to an unfamiliar resource landscape and find new breeding sites. Relocation may be costly and could compromise reproduction.MethodsHere, we explored how the Lesser black-backed gull (Larus fuscus), a colonial breeding seabird species with a wide ecological niche, responds to the loss of its breeding habitat. We investigated how individuals adjusted their foraging behaviour after relocating to another colony due to breeding site destruction, and whether there were any reproductive consequences in the first years after relocation. To this end, we compared offspring growth between resident individuals and individuals that recently relocated to the same colony due to breeding habitat loss. Using GPS-tracking, we further investigated the foraging behaviour of resident individuals in both colonies, as well as that of relocated individuals, as enhanced foraging effort could represent a potential driver of reproductive costs.ResultsWe found negative consequences of relocation for offspring development, which were apparent when brood demand was experimentally increased. Recently relocated gulls travelled further distances for foraging than residents, as they often visited more distant foraging sites used by residents breeding in their natal colony as well as new areas outside the home range of the residents in the colony where they settled.ConclusionsOur results imply that relocated individuals did not yet optimally adapt to the new food landscape, which was unexpected, given the social information on foraging locations that may have been available from resident neighbours in their new breeding colony. Even though the short-term reproductive costs were comparatively low, we show that generalist species, such as the Lesser black-backed gull, may be more vulnerable to habitat loss than expected. Long term studies are needed to investigate how long individuals are affected by their relocation in order to better assess potential population effects of (breeding) habitat loss.

This study investigated the distribution, numbers and conservation threats of the West African Crested Tern, which was recently elevated to full species after it was split from the Royal Tern with an American and African subspecies. In the period 1998–2019, a total of 13 West African coastal islands were identified as breeding localities, stretching from Mauritania to Guinea. All the islands are isolated, usually sandy and subject to erosion. There was great yearly variation in the numbers of breeding pairs within and between sites. A complete census of all breeding locations in 2015 and 2019 resulted in estimates of 79 000 and 77 000 pairs, respectively. The threats identified are predation, human disturbance, nest flooding and loss of breeding habitat as a result of coastal erosion. Predation of eggs and chicks by Sacred Ibises and especially Great White Pelicans may heavily impact on the species’ breeding output. Human disturbance is slight because most of the breeding islands are within protected areas. Flooding of nests has increasingly been observed in recent years, occurring at nine of 11 islands occupied by the terns in 2015. Most islands are subject to erosion, which has resulted in substantial loss of suitable breeding habitat over the 22-year study period. Two important islands have become completely unsuitable. We conclude that West African Crested Terns have an uncertain future. Food shortage resulting from industrial fishing is suspected, and the effects of climate change might negatively impact on habitat suitability and food availability. Monitoring of the total population at three-year intervals is recommended.

Numbers of eight seabird species that have bred in coastal areas of South Africa’s arid Northern Cape province have all shown substantial decreases since initial estimates of their abundance were made in the latter part of the twentieth century. Likely drivers of these decreases include reduced availability of food and the loss of suitable breeding habitat, including in the Orange River Estuary and at coastal pans and islands, which has resulted from a variety of human alterations, uses and disturbances. The decreases have contributed to a worsening conservation status of several of the seabirds, some of which are endemic to southern Africa. The more adaptable species appear to have partially offset habitat loss by moving to alternative breeding sites. However, substitute habitat is limited and the more numerous species suffered relatively large decreases. In order to conserve remnant populations it will be necessary to prevent further loss of breeding habitat, restore some former habitats and provide suitable, alternative habitat.

The loggerhead shrike (Lanius ludovicianus) is a grassland bird species whose preferred nesting habitat in eastern Canada is pastureland. This species has been extirpated from much of its historical range in this region, and breeding habitat loss is suspected to be an important cause of this decline. We evaluated the availability of suitable breeding habitats in Quebec using satellite imagery. Because this species no longer breeds in Quebec, we established habitat selection criteria from known nesting sites in the adjacent province of Ontario, from analysis of a Landsat-TM satellite image, and applied these criteria to Landsat-TM images covering southern Quebec. We developed regional landscape criteria in 100 km2 plots and patch indices criteria at the pasture level. Spatial analyses were conducted to characterize plots and pastures on the basis of pasture availability and spatial distribution. Pastures suitable for nesting loggerhead shrikes were those fulfilling patch criteria at the pasture level and located in plots fulfilling regional landscape criteria. Overall, 310 out of 1700 plots located in the historical breeding range of the loggerhead shrike in Quebec fulfilled landscape criteria, supporting 3988 pastures that fulfilled patch criteria. More than 500 of these pastures were visited to validate their current status. The Outaouais region would be the most suitable region for nesting loggerhead shrikes in southern Quebec, where suitable breeding habitat still remains because more than two-thirds of visited sites were still pastureland, hawthorns were well-distributed in the region, and pastureland fragmentation was lowest. We conclude that the availability of breeding habitat does not limit the establishment of a breeding population of loggerhead shrike in southern Quebec, as we estimated that thousands of hectares of suitable habitat still remain in that province.

Golden‐winged warblers (Vermivora chrysoptera) are facing population declines in the southern Appalachian Mountains. Breeding habitat loss is considered one of the primary reasons for golden‐winged warbler declines in the region. Expanding breeding habitat availability in a manner that promotes population expansion across an interconnected network of habitat patches is particularly problematic in a landscape dominated by private land ownership. We assessed the connectivity of golden‐winged warbler breeding habitat in a 29,680‐ha landscape with 5,664 ownership parcels between 2 state‐owned game lands in northwestern North Carolina, USA, in fall 2021. We created a connectivity map and provided examples of 3 means of prioritizing parcels for golden‐winged warbler habitat maintenance and management based on dispersal distances of fledglings that could return the following spring with prior familiarity of potential nesting areas. Prioritized parcels can guide land acquisition and conservation easement development as well as active management. Despite being highly parcelized, the area has both well‐connected and disjointed clusters of core habitat patches, but habitat management on privately owned parcels would be needed to connect core habitat patches to enable dispersing golden‐winged warbler fledglings to encounter potential breeding habitat that they could use the following spring.

Every year, millions of migratory shorebirds fly through the East Asian-Australasian Flyway between their arctic breeding grounds and Australasia. This flyway includes numerous coastal wetlands in Asia and the Pacific that are used as stopover sites where birds rest and feed. Loss of a few important stopover sites through sea-level rise (SLR) could cause sudden population declines. We formulated and solved mathematically the problem of how to identify the most important stopover sites to minimize losses of bird populations across flyways by conserving land that facilitates upshore shifts of tidal flats in response to SLR. To guide conservation investment that minimizes losses of migratory bird populations during migration, we developed a spatially explicit flyway model coupled with a maximum flow algorithm. Migratory routes of 10 shorebird taxa were modeled in a graph theoretic framework by representing clusters of important wetlands as nodes and the number of birds flying between 2 nodes as edges. We also evaluated several resource allocation algorithms that required only partial information on flyway connectivity (node strategy, based on the impacts of SLR at nodes; habitat strategy, based on habitat change at sites; population strategy, based on population change at sites; and random investment). The resource allocation algorithms based on flyway information performed on average 15% better than simpler allocations based on patterns of habitat loss or local bird counts. The Yellow Sea region stood out as the most important priority for effective conservation of migratory shorebirds, but investment in this area alone will not ensure the persistence of species across the flyway. The spatial distribution of conservation investments differed enormously according to the severity of SLR and whether information about flyway connectivity was used to guide the prioritizations. With the rapid ongoing loss of coastal wetlands globally, our method provides insight into efficient conservation planning for migratory species.

The migratory monarch butterflies (Danaus plexippus) of eastern North America have undergone large-scale declines, which may be attributable to a variety of underlying causes. The uncertainty about the primary cause of declines and whether individual threats are likely to increase in the future presents challenges for developing effective conservation management and policy initiatives that aim to improve population viability. This paper identifies five potential threats and classifies these threats according to the types of studies (observational, experimental, simulation/models) and their current impact and anticipated risk. Broadly, the threats can be classified into five categories: (1) change in suitable abiotic environmental conditions; (2) deforestation in the overwintering range; (3) exposure to contaminants including the bacteria Bacillus thuringiensis, herbicides, and insecticides; (4) loss of breeding habitat; and (5) predation, parasitism, and species-specific pathogens. The vast distribution of the monarch butterfly makes it likely that population declines are attributed to a suite of interacting factors that vary spatially and temporally in their contribution. Nonetheless, the published papers we reviewed suggest the decline in suitable environmental conditions in addition to overwintering (i.e., deforestation) and breeding habitat loss are the most likely threats to continue to affect the population viability of monarch butterflies.

Our objective was to determine whether changes in populations of forest-interior bird species were related to changes in extent of interior forest along Breeding Bird Survey (BBS) census routes in Massachusetts. We first identified a suite of 28 forest-interior bird species (FIA species), based on correlations between bird abundance (in 2003–2007) and extent of interior forest (in 2005) along BBS routes. From this group, we eliminated 13 species whose breeding habitats were described in the literature as including forest edge or second growth, resulting in a more stringently defined subset of 15 (FIB) species. We quantified the extent of forest and interior forest (>100 m from a forest edge) along BBS routes based on digitized aerial photographs from 1971, 1985, and 1999. We also quantified changes in abundance of the 28 forest bird species along BBS survey routes over the same time period. Overall, changes in abundance of FIB species paralleled changes in extent of interior forest, with 13 of 15 species showing positive correlations, 5 of which were significant. However, substantial variation occurred among species, including conspicuous declines in Hylocichla mustelina (Wood Thrush) and Piranga olivacea (Scarlet Tanager) and conspicuous increases in Vireo solitarius (Blue-headed Vireo) and Setophaga coronata (Yellow-rumped Warbler). Changes were not significantly related to either migratory status (Neotropical vs. other) or nest location (ground vs. arboreal). Several differences could be attributed to species-specific factors, such as reintroductions of Meleagris gallopavo (Wild Turkey) and Corvus corax (Common Raven) or introduction of competitors, such as Haemorhous mexicanus (House Finch) impacting Haemorhous purpureus (Purple Finch). Changes in some bird populations seem to reflect forest succession, e.g., Hylatomus pileatus (Pileated Woodpecker), while others are unexplained and may be due to changes on migratory routes or wintering grounds. Overall, loss of interior forest is an important incremental factor in forest bird population declines, although other factors had a greater impact in the period under study.

In reproduction, many animal species migrate to local habitats that are appropriate for reproduction and for growth of newly born offspring. The examples are ubiquitous among crabs, freshwater fishes, amphibians, migratory birds, and sea animals. We propose a basic equation for population dynamics of such animals, assuming that the number of offspring is proportional to the area of the local breeding habitats as a first approximation. This equation is very simple to be solved analytically, and useful for representing environmental issues of habitat destruction and degradation. According to the equation, the adult density in breeding habitats increases temporarily during habitat destruction and returns to the original density afterwards. The temporal peak value is higher for a larger proportion of area with destruction, a higher temporal rate of destruction, and a higher survival probability of the adults. In contrast, habitat degradation results simply in a decrease of the adult density in breeding habitats. Using this equation, we will discuss the vulnerability of populations to epidemic diseases due to temporal local high densities with decreasing breeding habitats by human activities, exemplifying an outbreak of cyprinid herpesvirus 3 for wild carps in Lake Biwa.

Imperiled species recovery is a high‐stakes endeavor where uncertainty surrounding effectiveness of conservation actions can be an impediment to implementation at necessary scales, especially where habitat restoration is required. Gunnison sage‐grouse (Centrocercus minimus) represents one such species in need of large‐scale habitat restoration. It is a federally threatened sagebrush (Artemisia spp.) obligate bird with a limited range in Colorado and Utah. Threats to recovery of Gunnison sage‐grouse include conifer expansion into sagebrush along with additional habitat loss and degradation attributed to human development and agricultural conversion. Recovery of Gunnison sage‐grouse and other sensitive species can be aided by spatial tools that forecast plausible outcomes of conservation actions. We illustrate this by using a novel framework for predicting outcomes of proactive tree removal and subsequent sagebrush restoration for the Gunnison sage‐grouse. To assess threats on Gunnison sage‐grouse lek presence, we developed a spatially explicit breeding habitat model to compare active lek and random pseudo‐absence locations from 2015. Models identified land cover, climatic, and abiotic variables at landscape‐level scales (0.56 and 4 km) most important for predicting breeding habitat. Our model correctly differentiated between lek and pseudo‐absence locations 94% of the time. All but one of the active leks (n = 94) were in areas with >0.65 probability of lek occurrence. Using this probability value as a threshold, we predicted 15% of the current grouse range as high‐quality breeding habitat. Simulated removal of trees in areas with ≤30% tree canopy cover (0.56‐km scale) increased extent of high‐quality habitat fourfold (59%). Hypothetical restoration of sagebrush cover in the same areas increased habitat quality an additional 11%. Our breeding habitat model indicated that targeted tree removal and sagebrush restoration have potential to improve Gunnison sage‐grouse breeding habitat. While our habitat treatment scenarios were not meant to be prescriptive, they highlight that considerable uplift in Gunnison sage‐grouse breeding habitat may be possible across much of its range with cooperation from multiple stakeholders and illustrates the utility of this approach for predicting biological return on investment.

For many migratory species the area of wintering or breeding habitat is changing or is likely to change as a result of processes such as habitat destruction or global environmental change. I show that the ratio of population decline to loss of typical wintering habitat equals d9/(d9 + b9), where d9 is the slope of relation between per capita winter mortality and population density and b9 is the slope of the relation between per capita net breeding output and population density. Similarly the ratio of population decline to loss of typical breeding habitat equals b9/(b9 + d9). Game theory models can be used to predict the values of b9 and d9. For example, incorporating values of d9 and b9 from such models for the oystercatcher Haematopus ostralegus shows that a loss of 1% of wintering habitat will result in a population decline of 0.69% while a loss of 1% of breeding habitat will result in a population decline of 0.31%.

Simple SummaryWe used pre-1990 climate envelopes and an ecosystem vulnerability model to forecast shifts in the extent of breeding habitats for eight owl species occurring in montane woodlands and forests of the southwestern US. For five of the eight species, the regional habitat extent was projected to decline by at least 60% by 2090. The steepest rates of habitat loss were predicted for the boreal owl (Aegolius funereus) and the flammulated owl (Psiloscops flammeolus). The boreal owl, which is absent in Arizona and at the trailing edge of its distribution in New Mexico, was projected to retain only about 15% of its mapped regional habitat by 2090. Generalist and lower-elevation owl species fared better in our model predictions, while the whiskered screech-owl (Megascops trichopsis) habitat was projected to contract locally yet expand to the north. The results of this study suggest high exposure to climate change impacts for Southwestern North America’s upper-elevation owls. Long-distance migration and low philopatry may prove important to some montane owl populations in adapting to the regional loss of montane woodland and forest habitats.The high-resolution forecasting of vegetation type shifts may prove essential in anticipating and mitigating the impacts of future climate change on bird populations. Here, we used the US Forest Service Ecological Response Unit (ERU) classification to develop and assess vegetation-based breeding habitat profiles for eight owl species occurring in the foothills and mountains of the Southwestern US. Shifts in mapped habitat were forecast using an ecosystem vulnerability model based on the pre-1990 climate envelopes of ERUs and the Intergovernmental Panel on Climate Change’s (IPCC) A1B moderate-emission scenario for the future climate. For five of the eight owl species, the regional breeding habitat extent was projected to decline by at least 60% by 2090. Three species, the boreal owl (Aegolius funereus; at the trailing edge of its distribution), flammulated owl (Psiloscops flammeolus), and northern pygmy-owl (Glaucidium gnoma), were projected to experience the steepest habitat loss rates of 85%, 85%, and 76%, respectively. Projected vegetation shifts overlaid with well-documented flammulated owl breeding populations showed the complete or near complete loss of habitat by 2090 in areas of montane forest currently supporting dense aggregations of owl territories. Generalist or lower-elevation owl species were predicted to be less impacted, while, for the whiskered screech-owl (Megascops trichopsis), the contraction of the current habitat was nearly offset by a projected northward expansion. In general, the results of this study suggest high exposure to climate change impacts for the upper-elevation forest owls of semi-arid Southwestern North America. Long-distance migration and low natal philopatry may prove important to some montane owl populations in adapting to the regional loss of habitat.

Breeding habitat loss and nest predation are considered the main causes of Snowy Plover (Charadrius nivosus) populations decline worldwide. We evaluated the effects of season, nest age, distance to nearest vegetation patch, distance to nearest body of water, habitat type, and nesting substrate on the daily survival rate of Snowy Plover nests. During 2014-2015, we located 84 nests in Las Garzas-Chahuin-Chihua lagoon in Marismas Nacionales, Nayarit, Mexico. We used MARK software to estimate daily nest survival rate, which was 0.969 (95% CI = 0.95 - 0.97) for both breeding seasons combined, with a 42% finite nesting success. A total of 44 nests (52%) were successful, while 40 (48%) failed. The main causes of nest failure were predation (n = 30; 75% of failed nests) and flooding (n = 9; 22.5% of failed nests); one nest was lost due to unknown causes (2.5%). Daily survival rate increased with nest age and distance from the nearest vegetation patch. By contrast, daily survival rate decreased with the progression of the breeding season; a higher probability of nest success was evident when established early in the breeding season. Our results show the importance of different positive and negative factors influencing nest survival that might be considered as part of conservation strategies.

Breeding habitat loss and depletion of genetic diversity can have critically negative impacts on species, and especially so for habitat specialists. The Aquatic Warbler Acrocephalus paludicola is a threatened European songbird that breeds in fens, which have been lost and fragmented over centuries. We used microsatellite loci to perform a spatial and longitudinal comparison, comparing samples collected recently (contemporary) with those obtained about two decades earlier (historical) from c. 25% of the breeding range (Biebrza and Polesie) of the Aquatic Warbler. With these data we explored changes in genetic diversity, expansions and reductions of population size, population structure, and gene flow. Allelic richness, expected heterozygosity, the number of effective and private alleles, and effective population size (NE ≈ 200) were low and comparable across time and space. We detected a genetic bottleneck in contemporary Biebrza, and a less certain bottleneck in both historical and contemporary Polesie. Across space, Biebrza and Polesie were not genetically differentiated in either period. All the historical samples clustered together, but in the contemporary samples a small part of Polesie clustered separately (FST = 0.011). Across time, Biebrza and Polesie showed low but significant differentiation (FST = 0.026–0.064), and historical and contemporary groups clustered apart. A principal coordinate analysis on genetic distance detected three groups, which spanned sampling locations. In the temporal comparison, the contemporary group and contemporary Biebrza had elevated mean within‐group pairwise relatedness. We did not recover signals for sex‐biased dispersal, asymmetric gene flow or isolation‐by‐distance using the molecular data. Our results suggest that the studied populations show: (1) impoverished genetic diversity, (2) a change in allele frequencies over the two decades studied and (3) high gene flow between distant breeding sites, implying high resilience to habitat fragmentation that should facilitate the success of recolonising restored habitat patches by Aquatic Warblers.

Simple SummaryTo understand the impact of climate change on marine mammals, we focused on the spotted seal population in the North Pacific. This ice-breeding species exhibits distinct variations across different regions. Our study aimed to quantify their ecological niches and conduct a conservation gap analysis. We found clear niche divergence among three populations and observed habitat contraction driven by climate change, potentially leading to breeding habitat loss in certain areas. Unfortunately, existing marine protected areas do not adequately cover most spotted seal habitats. By incorporating local adaptation into species distribution modeling, our research provides valuable insights for designing effective conservation policies to protect the different geographical populations of spotted seals in the face of climate change. This study highlights the importance of considering local adaptation in conservation and management strategies for marine mammal species.Local adaptation has been increasingly involved in the designation of species conservation strategies to response to climate change. Marine mammals, as apex predators, are climatechange sensitive, and their spatial distribution and conservation requirements are critically significant for designing protection strategies. In this study, we focused on an ice-breeding marine mammal, the spotted seal (Phoca largha), which exhibits distinct morphological and genetic variations across its range. Our objectives were to quantify the ecological niches of three spotted seal populations, construct the species-level model and population-level models that represent different regions in the Bering population (BDPS), Okhotsk population (ODPS) and southern population (SDPS), and conduct a conservation gap analysis. Our findings unequivocally demonstrated a clear niche divergence among the three populations. We predicted habitat contraction for the BDPS and ODPS driven by climate change; in particular, the spotted seals inhabiting Liaodong Bay may face breeding habitat loss. However, most spotted seal habitats are not represented in existing marine protected areas. Drawing upon these outcomes, we propose appropriate conservation policies to effectively protect the habitat of the different geographical populations of spotted seals. Our research addresses the importance of incorporating local adaptation into species distribution modeling to inform conservation and management strategies.