Are life history events of a northern breeding population of Cooper's Hawks influenced by changing climate?

Numerous studies have demonstrated earlier timing of spring migration and egg‐laying in small passerines, but documentation of such responses to recent climate change in the life histories of higher trophic feeding birds such as raptors is relatively scarce. Raptors may be particularly susceptible to possible adverse effects of climate change due to their longer generation turnover times and lower reproductive capacity, which could lead to population declines because of an inability to match reproductive timing with optimal brood rearing conditions. Conversely adaptively favorable outcomes due to the influence of changing climate may occur. In general, birds that seasonally nest earlier typically have higher reproductive output compared to conspecifics that nest later in the season. Given the strong seasonal decline in reproductive output, and the heritability of nesting phenology, it is possible that nesting seasons would (adaptively) advance over time. Recent climate warming may release prior ecological constraints on birds that depend on food availability at the time of egg production, as do various raptors including Cooper's Hawks (Accipiter cooperii). Under this scenario, productivity, especially clutch size, might increase because it is likely that this reproductive demographic may be the most immediate response to the earlier seasonal presence of food resources. We demonstrated a statistically significant shift of about 4–5 days to an earlier timing of egg‐hatching in spring across 36 years during 1980–2015 for a partially migratory population of Cooper's Hawks in Wisconsin, United States, which is consistent with a recent study that showed that Cooper's Hawks had advanced their timing of spring migration during 1979–2012. Both studies occurred in the Great Lakes region, an area that compared to global averages is experiencing earlier and increased warming particularly in the spring in Wisconsin. The nesting period did not lengthen. We suggest that the gradual shift of six consecutive generations of hawks was likely in response to recent climate change or warming. We did not detect any long‐term temporal change in average clutch or brood sizes. However, such indices of reproduction are among the highest known for the species and thus may be at their physio‐ecological maximum for this population. Our study population appears to show resilience to and does not appear to be adversely influenced by the recent rate of changing climate at this time.     

Population structure and genetic diversity in Swainson’s Hawks (Buteo swainsoni): implications for conservation

Swainson’s Hawks (Buteo swainsoni) are large raptors with a breeding distribution extending across much of western North America where they were historically considered one of the most abundant raptors. Swainson’s Hawks have declined precipitously in many parts of their range during the 20th century, and the historical range in California has been much reduced. In the Central Valley of California (CV), Swainson’s Hawks exhibit behavioral and morphological characteristics apparently different from other regions. To describe the genetic diversity and population structure of Swainson’s Hawks throughout their range, 19 microsatellite loci and 416 base pairs of the mitochondrial control region were analyzed. Microsatellite diversity appears high throughout the contemporary range. A Bayesian model-based analysis of microsatellite genotypes revealed clusters associated with the CV and the Great Basin/Great Plains region of North America (GBGP) with overlap between regions. F _ST estimates suggest limited differentiation among Swainson’s Hawks with isolation by distance. A heterozygote excess indicated a recent reduction in effective population size of Swainson’s Hawks across all regions. Control region data revealed no population structure and provided evidence of historic population expansion in the GBGP. In the CV a weaker signature of population expansion was detected, possibly altered by recent declines. While genetic data suggests recent gene-flow across regions, apparent differences between the CV and GBGP in traits with potential fitness consequences (migratory behavior and morphology) along with marked decline in numbers in California call for careful conservation, management, and monitoring of Swainson’s Hawks in the CV.     

Improving conservation strategies of raptors through landscape ecology analysis: The case of the endemic Cuban Black Hawk

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An analysis of Bat Hawk Macheiramphus alcinus diet in the Melaky Region of lowland western Madagascar

We present information on the prey taken by the Bat Hawk Macheiramphus alcinus in two different areas of lowland western central Madagascar. These are the first dietary data from Madagascar for this widespread Old World species. The recovered remains were almost exclusively of bats and birds, with a few examples of reptiles and insects. In total, 178 pellets were analysed. On the basis of minimum number of individuals and biomass, bats accounted for 58.3% and 30.3%, respectively, and birds 36.1% and 69.7%, respectively. Amongst the nine species of bats recovered from the pellets, four were represented by multiple individuals, particularly taxa belonging to the families Molossidae and Vespertilionidae that fly in open areas, and for the 11 species of identified birds, all were represented by a single individual. These patterns are interpreted as a specialisation of feeding on bats during a narrow window of time at dusk, as they leave day roost sites, and then using birds in a more general manner to fill in nutritional needs.     

Comparative phylogeography and population genetics within Buteo lineatus reveals evidence of distinct evolutionary lineages

Traditional subspecies classifications may suggest phylogenetic relationships that are discordant with evolutionary history and mislead evolutionary inference. To more accurately describe evolutionary relationships and inform conservation efforts, we investigated the genetic relationships and demographic histories of Buteo lineatus subspecies in eastern and western North America using 21 nuclear microsatellite loci and 375-base pairs of mitochondrial control region sequence. Frequency based analyses of mitochondrial sequence data support significant population distinction between eastern (B. l. lineatus/alleni/texanus) and western (B. l. elegans) subspecies of B. lineatus. This distinction was further supported by frequency and Bayesian analyses of the microsatellite data. We found evidence of differing demographic histories between regions; among eastern sites, mitochondrial data suggested that rapid population expansion occurred following the end of the last glacial maximum, with B. l. texanus population expansion preceding that of B. l. lineatus/alleni. No evidence of post-glacial population expansion was detected among western samples (B. l. elegans). Rather, microsatellite data suggest that the western population has experienced a recent bottleneck, presumably associated with extensive anthropogenic habitat loss during the 19th and 20th centuries. Our data indicate that eastern and western populations of B. lineatus are genetically distinct lineages, have experienced very different demographic histories, and suggest management as separate conservation units may be warranted.     

Nutritional condition and serum biochemistry for free-living Swainson's Hawks wintering in central Argentina

We assessed the nutritional condition and established reference values for serum chemistry parameters in a long distance migrant bird of prey, the Swainson's Hawk (Buteo swainsoni), wintering in central Argentina. We analyzed serum concentration of urea, uric acid, cholesterol, and triglycerides and assessed age and sex related differences in these parameters. A body condition index was obtained from the resultant residuals of the regression of body mass and a morphometric measure. No statistical differences were observed among sex and age groups for urea, uric acid and triglyceride serum concentration. However, cholesterol concentration differed among male and female hawks, which could be related to the gain of body mass in wintering grounds at differential rates. The mean values of the four parameters were in the range of those recorded in the Common Buzzard (Buteo buteo), indicating good nutritional condition of the population we studied. Forearm length was the morphometric variable that better correlated with body mass. The resultant body condition index was only correlated with triglyceride concentration, suggesting that this index could be valuable in future work dealing with the assessment of body fat storage in wintering and breeding hawks, as well as in stopover points on the migratory route.     

Visual position stabilization in the hummingbird hawk moth, Macroglossum stellatarum L. II. Electrophysiological analysis of neurons sensitive to wide-field image motion

Response properties of neurons in the cervical connectives of the hummingbird hawk moth, Macroglossum stellatarum L., were determined. All neurons described in this account respond directionally selectively to motion in large parts of the visual field of either eye. They respond maximally to bilateral stimulation, preferring either motion as induced on the eyes during translatory movements of the animal or when it turns around one of its body axes. Cells most sensitive to rotational motion either respond best to rotation of the patterns around the vertical axis of the animal or around its longitudinal body axis. Neurons most sensitive to translational pattern motion respond best to either simulated translations of the animal along its vertical or along an oblique axis. Most types of neurons respond tonically and do not habituate. The sensitivity to motion stimuli is not evenly distributed within the receptive field of any investigated neuron. Part of these neurons might play a role in visual position and course stabilization. Accepted: 13 August 1997     

Sex determination of Red-tailed Hawks (Buteo jamaicensis calurus) using DNA analysis and morphometrics

ABSTRACT.   Currently, the sex of Red-tailed hawks ( Buteo jamaicensis ) cannot be determined by in-hand methods. Males and females do not differ in plumage and overlap in size. We collected feather samples and morphological measurements from migrating birds at four sites in the western United States. Sex was determined for individual birds using sex-specific DNA markers and polymerase chain reaction was used to identify these DNA markers. Using discriminant function analysis, we created equations for determining the sex of Red-tailed Hawks using in-hand measurements based on the DNA-determined sexes. We formed two equations, one for adults that was 98% accurate, and one for hatch-year birds that was 97% accurate. The ability to determine the sex of western Red-tailed Hawks using morphological measurements will be useful to investigators examining possible intra- or intersexual differences.