Fine-scale movement decisions of tropical forest birds in a fragmented landscape

The persistence of forest-dependent species in fragmented landscapes is fundamentally linked to the movement of individuals among subpopulations. The paths taken by dispersing individuals can be considered a series of steps built from individual route choices. Despite the importance of these fine-scale movement decisions, it has proved difficult to collect such data that reveal how forest birds move in novel landscapes. We collected unprecedented route information about the movement of translocated forest birds from two species in the highly fragmented tropical dry forest of Costa Rica. In this pasture-dominated landscape, forest remains in patches or riparian corridors, with lesser amounts of living fencerows and individual trees or "stepping stones." We used step selection functions to quantify how route choice was influenced by these habitat elements. We found that the amount of risk these birds were willing to take by crossing open habitat was context dependent. The forest-specialist Barred Antshrike (Thamnophilus doliatus) exhibited stronger selection for forested routes when moving in novel landscapes distant from its territory relative to locations closer to its territory. It also selected forested routes when its step originated in forest habitat. It preferred steps ending in stepping stones when the available routes had little forest cover, but avoided them when routes had greater forest cover. The forest-generalist Rufous-naped Wren (Campylorhynchus rufinucha) preferred steps that contained more pasture, but only when starting from non-forest habitats. Our results showed that forested corridors (i.e., riparian corridors) best facilitated the movement of a sensitive forest specialist through this fragmented landscape. They also suggested that stepping stones can be important in highly fragmented forests with little remaining forest cover. We expect that naturally dispersing birds and species with greater forest dependence would exhibit even stronger selection for forested routes than did the birds in our experiments

Landscape and Traffic Factors Influencing Deer–Vehicle Collisions in an Urban Enviroment

Deer–vehicle collisions (DVCs) are steadily increasing across North America. The increase is particularly pronounced in urban green spaces where deer (Odocoileus spp.) populations and road densities are high. In the greater city of Edmonton, Alberta, Canada, 333 DVCs occurred from 2002 to 2004. To identify landscape and traffic correlates of these collisions, we built 3 statistical models. The first model assessed the importance of local variables and was based on a spatial precision of the nearest intersection to which collisions were referenced. The second model was based on landscape characteristics and used the nearest township intersection to aggregate collisions. For each of the models, we generated an equivalent number of random locations in a geographic information system (GIS) and examined several independent variables at 4 spatial scales (using 100-m, 200-m, 400-m, and 800-m radius buffers). We used multivariate logistic regression to determine which landscape and traffic factors increased the probability of a DVC. The third model used ordinal regression to assess correlates with collision frequency. Our first (High Precision) model showed that DVCs occurred in areas with high speed limits and low densities of roads within an 800-m buffer. The second (Aggregate) model found DVCs more likely to occur in areas close to water and the combination of high road densities and non-forested vegetation of high productivity within 800 m. The third (Hotspot) model identified only high traffic speed as a correlate of collision frequency. A temporal analysis of the collision data found that DVCs peaked in mid November. We conclude that rates of DVCs could be reduced and road safety improved by lowering speed limits during peak seasons, particularly in areas where road density is high (i.e., interchanges) and where non-forested vegetation occurs in close proximity to roads. Several aspects of our analyses and results may have applications in other jurisdictions where DVCs occur

Flexibility in Animal Signals Facilitates Adaptation to Rapidly Changing Environments

Charles Darwin posited that secondary sexual characteristics result from competition to attract mates. In male songbirds, specialized vocalizations represent secondary sexual characteristics of particular importance because females prefer songs at specific frequencies, amplitudes, and duration. For birds living in human-dominated landscapes, historic selection for song characteristics that convey fitness may compete with novel selective pressures from anthropogenic noise. Here we show that black-capped chickadees (Poecile atricapillus) use shorter, higher-frequency songs when traffic noise is high, and longer, lower-frequency songs when noise abates. We suggest that chickadees balance opposing selective pressures by use low-frequency songs to preserve vocal characteristics of dominance that repel competitors and attract females, and high frequency songs to increase song transmission when their environment is noisy. The remarkable vocal flexibility exhibited by chickadees may be one reason that they thrive in urban environments, and such flexibility may also support subsequent genetic adaptation to an increasingly urbanized world

Physiology, behavior, and conservation

Many animal populations are in decline as a result of human activity. Conservation practitioners are attempting to prevent further declines and loss of biodiversity as well as to facilitate recovery of endangered species, and they often rely on interdisciplinary approaches to generate conservation solutions. Two recent interfaces in conservation science involve animal behavior (i.e., conservation behavior) and physiology (i.e., conservation physiology). To date, these interfaces have been considered separate entities, but from both pragmatic and biological perspectives, there is merit in better integrating behavior and physiology to address applied conservation problems and to inform resource management. Although there are some institutional, conceptual, methodological, and communication-oriented challenges to integrating behavior and physiology to inform conservation actions, most of these barriers can be overcome. Through outlining several successful examples that integrate these disciplines, we conclude that physiology and behavior can together generate meaningful data to support animal conservation and management actions. Tangentially, applied conservation and management problems can, in turn, also help advance and reinvigorate the fundamental disciplines of animal physiology and behavior by providing advanced natural experiments that challenge traditional frameworks

Mammals adjust diel activity across gradients of urbanization

Time is a fundamental component of ecological processes. How animal behavior changes over time has been explored through well-known ecological theories like niche partitioning and predator–prey dynamics. Yet, changes in animal behavior within the shorter 24-hr light–dark cycle have largely gone unstudied. Understanding if an animal can adjust their temporal activity to mitigate or adapt to environmental change has become a recent topic of discussion and is important for effective wildlife management and conservation. While spatial habitat is a fundamental consideration in wildlife management and conservation, temporal habitat is often ignored. We formulated a temporal resource selection model to quantify the diel behavior of 8 mammal species across 10 US cities. We found high variability in diel activity patterns within and among species and species-specific correlations between diel activity and human population density, impervious land cover, available greenspace, vegetation cover, and mean daily temperature. We also found that some species may modulate temporal behaviors to manage both natural and anthropogenic risks. Our results highlight the complexity with which temporal activity patterns interact with local environmental characteristics, and suggest that urban mammals may use time along the 24-hr cycle to reduce risk, adapt, and therefore persist, and in some cases thrive, in human-dominated ecosystems

Mammal responses to global changes in human activity vary by trophic group and landscape

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.Peer reviewe

Mechanisms of brood reduction in Fiordland crested penguins (Eudyptes pachyrhynchus)

Mechanisms of brood reduction were studied in Fiordland crested penguins (Eudyptes pachyrhynchus) on Open Bay Islands from July through October 1989. I quantified behavioural and environmental causes of egg and chick loss at the time of laying, during incubation, and after hatching to evaluate hypotheses advanced to explain the unique patterns of hatching asynchrony and egg dimorphism in eudyptid penguins. Although first eggs experienced lower survival than second eggs and most losses occurred during the laying interval, aggression between adult penguins did not appear to contribute to egg loss at any time. Similarly, egg mortality was not influenced by the effects of nest crowding or cover, or by the degree of intraclutch egg dimorphism. Egg temperatures were measured throughout the incubation period with thermocouples implanted in preserved eggs. Recorded temperatures increased markedly after the laying of the second natural egg, but did not differ between eggs of different sizes within a nest. First eggs were not consistently incubated in the anterior nest position and that position did not confer a thermal disadvantage. However, first eggs hatched later than second eggs. Retarded brood patch development may contribute to lower egg temperatures during the laying interval. Chicks from larger, second-laid eggs were larger at hatching, and grew more rapidly than their siblings. Overt aggression between feeding chicks was not observed and begging and feeding rates appeared to be similar. Nonetheless, large chicks experienced higher survival to the creche stage. Intra-clutch egg dimorphism was negatively correlated with the number of days two chicks survived in the same nest, but there was no relationship between survival and hatching asynchrony

Iridescent coloration of Tree Swallows relates to environmental metal pollution

Ornamental coloration in birds has been identified as a powerful, noninvasive tool for identifying exposure to metal pollution. Despite this potential, few studies have examined the effects of metals on iridescent coloration or assessed related impacts on bird fitness. Iridescent coloration is likely to be sensitive to metal pollution because it is already known to affect melanin production and this form of coloration is produced when light is refracted through layers of keratin and melanin inside feather barbules. In this study, we measured variation in plumage coloration, health (via oxidative stress), and reproductive success (via number of young fledged) of Tree Swallows (Tachycineta bicolor) nesting adjacent to water bodies containing different levels of metal pollution. Plumage hue shifted from bluer to greener and feather brightness was greater, where concentrations of copper and zinc were higher. Both patterns would be expected from changes in the microstructure of the feathers. Unexpectedly, increasing exposure to these metals correlated with increased apparent health (lower oxidative stress) in female swallows, but not males. Number of young fledged decreased slightly with exposure to metals but did not vary with the color of parents. Our results suggest the relationships between ornamental color, including iridescence, and fitness metrics are complex and much more work will be needed before color of iridescent feathers can provide a proactive, noninvasive, and effective diagnostic tool for detecting subtle effects of pollution on birds

Cumulative Effects of Barriers on the Movements of Forest Birds

Although there is a consensus of opinion that habitat fragmentation has deleterious effects on animal populations, primarily by inhibiting dispersal among remaining patches, there have been few explicit demonstrations of the ways by which degraded habitats actually constrain individual movement. Two impediments are primarily responsible for this paucity: it is difficult to separate the effects of habitat fragmentation (configuration) from habitat loss (composition), and conventional measures of fragmented habitats are assumed to be, but probably are not, isotropic. We addressed these limitations by standardizing differences in forest cover in a clearly anisotropic configuration of habitat fragmentation by conducting a homing experiment with three species of forest birds in the Bow Valley of Banff National Park, Canada. Birds were translocated (1.2-3.5  km) either parallel or perpendicular to four/five parallel barriers that are assumed to impede the cross-valley travel of forest-dependent animals. Taken together, individuals exhibited longer return times when they were translocated across these barriers, but differences among species suggest a more complex interpretation. A long-distance migrant (Yellow-rumped Warbler, Dendroica coronata) behaved as predicted, but a short-distance migrant (Golden-crowned Kinglet, Regulus satrapa) was indifferent to barrier configuration. A resident (Red-breasted Nuthatch, Sitta canadensis) exhibited longer return times when it was translocated parallel to the barriers. Our results suggest that an anisotropic arrangement of small, open areas in fragmented landscapes can have a cumulative barrier effect on the movement of forest animals, but that both modelers and managers will have to acknowledge potentially counterintuitive differences among species to predict the effect that these may have on individual movement and, ultimately, dispersal

Caching behaviour by red squirrels may contribute to food conditioning of grizzly bears

We describe an interspecific relationship wherein grizzly bears (Ursus arctos horribilis) appear to seek out and consume agricultural seeds concentrated in the middens of red squirrels (Tamiasciurus hudsonicus), which had collected and cached spilled grain from a railway. We studied this interaction by estimating squirrel density, midden density and contents, and bear activity along paired transects that were near (within 50 m) or far (200 m) from the railway. Relative to far ones, near transects had 2.4 times more squirrel sightings, but similar numbers of squirrel middens. Among 15 middens in which agricultural products were found, 14 were near the rail and 4 subsequently exhibited evidence of bear digging. Remote cameras confirmed the presence of squirrels on the rail and bears excavating middens. We speculate that obtaining grain from squirrel middens encourages bears to seek grain on the railway, potentially contributing to their rising risk of collisions with trains