Hawk Mountain Sanctuary Research Articles

Evidence of Continuing Downward Trends in American Kestrel Populations and Recommendations for Research into Causal Factors

ABSTRACT We analyzed long-term datasets from nest box programs, Breeding Bird Surveys run by the US Geological Survey, Christmas Bird Counts run by the National Audubon Society, and counts from two key fall migration watch sites, Hawk Mountain Sanctuary and Cape May Hawkwatch. We found that populations of American Kestrels (Falco sparverius) in North America are generally still declining, albeit with some caveats. Some populations are actually increasing, while others are remaining stable. Overall, the magnitude of annual change appears to be decreasing slightly during recent years. To understand potential causes of the decline, we recommend the following courses of action in no particular order: (1) determine whether the increase in Cooper's Hawk (Accipiter cooperii) populations is restricting kestrel distributions by the mere presence of the larger raptor; (2) study the effects of habitat loss and/or degradation on the falcon's wintering range; (3) further investigate on a broader spatial scale whether within-season habitat alterations are creating ecological traps for breeding kestrels; (4) determine the importance of arthropods in the diet of kestrels, especially the long-term population trends and timing of emergence of grasshoppers in relation to kestrel breeding chronology; (5) discover whether rodenticides pose a serious risk to American Kestrels across North America; (6) learn more about possible effects, both direct and indirect, that the use of neonicotinoids may have on kestrels; and (7) continue ongoing studies of the effect of climate change on these birds.

Acoustic bat survey kiosk for public outreach and research

Abstract The negative stereotypes and myths associated with bats can adversely affect efforts toward their conservation. A way to overcome these preconceived notions is through environmental education and public outreach. The goal of this project was to establish a system for monitoring bat activity at Hawk Mountain Sanctuary, with a component of environmental education included. This was accomplished through the establishment of a bat acoustic detector at Hawk Mountain Nature Center that was linked to a publicly accessible, interactive kiosk. The Hawk Mountain Bat Kiosk runs automated species identification software that compiles nightly bat activity into reports so that visitors can learn about the bat species that were present in the area the night before. The data were saved and analyses run to determine activity trends, indices of diversity, and species richness. We hope to establish additional kiosks to continue monitoring bats and provide public outreach for bat conservation education.

Purely sequential bounded-risk point estimation of the negative binomial means under various loss functions: Multi-sample problems

ABSTRACTA negative binomial (NB) distribution is often used to model over dispersed count data arising from areas including ecology, agriculture, health, etc. We have designed purely sequential bounded-risk methodologies to (1) simultaneously estimate an unknown k-vector of NB means and (2) estimate the difference in means of two independent NB populations under different forms of loss functions including customary and modified Linex loss as well as squared error loss. We have developed point estimation techniques both when (i) the thatch parameters τis are assumed known or unknown and (ii) the sample sizes are equal or unequal. The proposed methodologies are shown to satisfy interesting desirable properties including first-order asymptotic efficiency and first-order asymptotic risk efficiency. Summaries are provided from extensive sets of simulations showing encouraging performances of the proposed methodologies for both small and moderate sample sizes. These are followed by illustrations obtained by implementing each estimation strategy using real data from statistical ecology: Raptor count data of different species of raptors at the Hawk Mountain sanctuary in Pennsylvania.

Increase in Numbers and Potential Phenological Adjustment of Ruby-throated Hummingbirds (Archilochus colubris) during Autumn Migration at Hawk Mountain Sanctuary, Eastern Pennsylvania, 1990–2014

ABSTRACT Global change can affect several aspects of bird biology, including population size and migration timing. We used count data collected during 25 years (1990–2014) at Hawk Mountain Sanctuary, a raptor migration watch-site in eastern Pennsylvania, to investigate population changes in Ruby-throated Hummingbirds (Archilochus colubris) and the timing of their autumn migration, in light of ongoing climate change. Hummingbird numbers increased significantly from 1990–2014. The first 5%-, 50%-, 95%- and average passage dates of hummingbirds over this time indicated an earlier passage, with the first 5% passage-date shifting earlier significantly. Passage duration (number of days between 5% and 95% of the flight) remained relatively constant from 1990–2014. In light of similar shifts in timing of spring passage of this species, our results suggest that Ruby-throated Hummingbirds may be shifting the timing of their migratory cycle.

Relationship Between the North Atlantic Oscillation and Spring Migration Phenology of Broad-Winged Hawks (Buteo platypterus) At Hawk Mountain Sanctuary, 1998–2013

Abstract Climatic factors influence migration behavior in both short- and long-distance migratory birds. The Broad-winged Hawk (Buteo platypterus) is a long-distance migrant that exhibits a regular calendar-like migration pattern, with some interannual variability during both the northbound and southbound migrations. We examined the relationship between the North Atlantic Oscillation (NAO) and the timing of spring migration in Broad-winged Hawks based on standardized migration count data collected at Hawk Mountain Sanctuary from 1998 to 2013. A strong negative correlation was found between a higher April NAO index and earlier passage dates for the first 50% (r = −0.723, P < 0.01) and 95% (r = −0.565, P = 0.02) and mean passage date (r = −0.730, P < 0.01) of the hawks passing the watchsite. The April NAO values may serve as a useful indicator of the conditions encountered by Broad-winged Hawks during their northbound migration and our analyses suggest a possible climatic effect on their migration t...

Dispatches

Dispatches

“Typically American”

“Typically American”

A long-term database on raptor migration at Hawk Mountain Sanctuary, northeastern United States

In most northern temperate regions diurnal birds of prey, or raptors, migrate seasonally between their breeding and wintering grounds. Although their populations can be logistically difficult to survey and monitor because the birds are largely secretive and wide-ranging, most raptors are obligate or facultative soaring migrants that congregate along major thermal and orographic updraft corridors during their seasonal movements. Hawk Mountain Sanctuary (41° N, 75° W), which straddles the Kittatinny Ridge, the southernmost ridge in the Appalachian Mountains in eastern Pennsylvania, witnesses large numbers of migrating raptors during autumn migration. The Sanctuary's long-term migration-count database is the oldest detailed archive on the timing and magnitude of migratory raptors in the world. Records comprise daily (1934–1965) or hourly (1966–present) counts of 18 North American species of raptors migrating past the Sanctuary, as well as detailed weather data recorded from the lookout during autumn migratio...

How Fast Can a Falcon Dive?: Fascinating Answers to Questions about Birds of Prey. Animal Q&amp;A: Fascinating Answers to Questions about Animals. By Peter Capainolo and Carol A. Butler. New Brunswick (New Jersey): Rutgers University Press. $21.95 (paper). xix + 219 p. + 8 pl.; ill.; index. ISBN: 978‐0‐8135‐4790‐9. 2010.

Previous articleNext article No AccessReviews and Brief NoticesHow Fast Can a Falcon Dive?: Fascinating Answers to Questions about Birds of Prey. Animal Q&A: Fascinating Answers to Questions about Animals. By Peter Capainolo and Carol A. Butler. New Brunswick (New Jersey): Rutgers University Press. $21.95 (paper). xix + 219 p. + 8 pl.; ill.; index. ISBN: 978‐0‐8135‐4790‐9. 2010.Laurie GoodrichLaurie GoodrichHawk Mountain Sanctuary Association, Kempton, Pennsylvania Search for more articles by this author Hawk Mountain Sanctuary Association, Kempton, PennsylvaniaPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 86, Number 4December 2011 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/662489 Views: 2Total views on this site Copyright © 2011 by The University of Chicago Press. All rights reserved.PDF download Crossref reports no articles citing this article.

Rosalie Edge, Hawk of Mercy: The Activist Who Saved Nature from the Conservationists

The career of Mabel Rosalie Barrow Edge (1877–1962) as a conservation activist began when she was in her early fifties. The founder of the Emergency Conservation Committee (ECC), Edge campaigned to end the use of poison for wildlife control, and she exposed the conflicts of interest in private and government organizations while also advocating for the establishment of two new national parks and the preservation of sugar pines at Yosemite National Park. Along the way she created Hawk Mountain Sanctuary in Pennsylvania and argued against the National Audubon Society's for-profit trapping of animals in its refuges. Edge was a multitasking conservation activist. Using previously unavailable primary sources, Dyana Z. Furmansky offers an engaging portrait of Edge as activist while piecing together the story of Edge as a daughter, wife, mother, friend, and colleague. In the 1930s William Temple Hornaday called Edge “the only woman in conservation” (p. 218); Edge's son Peter gave Furmansky a suitcase filled with his mother's papers to recover “a forgotten bit of history” (p. xiii).

Site fidelity and lifetime territorial consistency of Ovenbirds (Seiurus aurocapilla) in a contiguous forest

ABSTRACT. We investigated territory-level habitat use patterns of 132 color-banded male Ovenbirds (Seiurus aurocapilla) over a 12-year period at Hawk Mountain Sanctuary in eastern Pennsylvania. Our primary goals were to test hypotheses concerning selection behavior as well as to describe territory fidelity of an area-sensitive Neotropical migrant by quantifying year-to-year movements of individuals over a period equivalent to several generations. Furthermore, we tested whether returns and territory shifts were associated with prior reproductive success and bird age. We measured occupancy as the number of birds that occupied 60-m grid cells that covered two 18-ha study sites over the 12-year period and similarly calculated rates of reproductive success within each grid cell. Rates of reproductive success were generally high (>60%) and were not correlated with occupancy rates. Return rates also were high, and birds rarely moved far from their first territory (mean = 68 m) during their lifetimes. There was n...

In Memoriam: Gary Bortolotti, 1954–2011

The Auk, Vol. , Number , pages −. ISSN -, electronic ISSN -. ©  by The American Ornithologists’ Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Rights and Permissions website, http://www.ucpressjournals. com/reprintInfo.asp. DOI: ./auk.... Gary Bortolotti, AOU member since , Elective Member () and Fellow (), was born on  August  in Smith’s Falls, Ontario. Gary was stricken with acute myelogenous leukemia late in May , which, with the subsequent chemotherapy, left him severely immunocompromised. Further complications from a severe respiratory infection led to his sudden death on  July . Gary grew up in Toronto, where he attended Northview Heights Collegiate in North York. He obtained a BSc. in forestry at the University of Toronto (). While working on his forestry degree, he became more interested in birds than in the trees. He switched to zoology and, with the support of a series of fellowships and grants from Hawk Mountain Sanctuary, the National Wildlife Federation, the World Wildlife Fund, the Eagle Foundation, and the Natural Sciences and Engineering Research Council of Canada (NSERC), became a doctoral student. Gary worked under Jon C. Barlow on evolution of the growth rate and nestling sex ratio The Auk 128(4):798–799, 2011 © The American Ornithologists’ Union, 2011. Printed in USA.

Annual Variation in West Nile Virus Antibodies in American Kestrels (Falco sparverius) in Eastern Pennsylvania

Abstract American Kestrels (Falco sparverius) nesting near Hawk Mountain Sanctuary in eastern Pennsylvania exhibited widespread West Nile virus (WNV) seroprevalence in 2004. Here we examine the dynamics of WNV in kestrels nesting near Hawk Mountain Sanctuary in 2004–06. We tested kestrel saliva for viral RNA using oral swabs analyzed by RT-PCR, and all swabs were negative for WNV. We used plaque-reduction neutralization testing (PRNT) to measure WNV antibodies in serum. In 2004, we tested 22 adult kestrels and most (95%) were positive for WNV. In 2005, we tested blood samples from six adults and seven nestlings, and WNV seroprevalence was 33% in adults and 14% in nestlings. In 2006, we sampled seven adults and eight nestlings, and 29% of the adults and no nestlings were positive. WNV was widespread in birds, mosquitoes, and humans in Pennsylvania in 2003, and subsequently has declined in these populations. The prevalence of WNV antibodies in the kestrels was compared to surveillance data for mosquitoes, d...

Detecting Population Trends in Migratory Birds of Prey

Abstract Counts of visible migrants at traditional watchsites throughout North America provide an opportunity to augment population-monitoring efforts for birds of prey. We analyzed hourly counts of migrating raptors at one inland (Hawk Mountain Sanctuary, Pennsylvania) and one coastal (Cape May Point, New Jersey) watchsite in northeastern North America. Hourly counts of migrants have been collected for 38 years at Hawk Mountain Sanctuary and for 28 years at Cape May Point. We compared effort-adjusted, arithmetic-mean passage rates to five geometric-mean indexes for 12 species. We used reparameterized polynomial regression to estimate trends in the indexes and to test the significance of trends from 1976–1978 (average index over three-year period) to 2001–2003. Effort-adjusted, arithmetic-mean indexes corresponded to more sophisticated indexes on the complete data sets but did not perform well on simulated data with missing observation days. We recommend the use of a regression-based, date-adjusted index for the analysis of hawk-count data. This index produced trends similar to other geometric-mean indexes, performed well on data sets simulating reduced sampling frequency, and outperformed other indexes on data sets with large blocks of missing observation days. Correspondence between trends at the watchsites and trends from Breeding Bird Surveys (BBSs) suggests that migration counts provide robust estimates of population trends for raptors. Furthermore, migration counts allow the monitoring of species not detected by BBS and produce trends with greater precision for species sampled by both methods. Analysis of migration counts with appropriate methods holds considerable promise for contributing to the development of integrated strategies to monitor raptor populations. Detección de Tendencias Poblacionales en Aves de Presa Migratorias

Prevalence of West Nile Virus Antibodies in a Breeding Population of American Kestrels (Falco sparverius) in Pennsylvania

West Nile virus (WNV) has been identified in nearly 300 species of wild birds, including raptors, in North America since its introduction in New York City in 1999. American Kestrels (Falco sparverius) are susceptible to WNV infection, and the numbers of these birds have declined along the Atlantic coast in recent years. We examined the population biology and WNV exposure of kestrels breeding in the area surrounding Hawk Mountain Sanctuary in Kempton, Pennsylvania, USA. The reproductive biology of kestrels in this area was studied from 1992 until 2004. The number of kestrels breeding in nestboxes in 2004 was only 44% of the 6-yr mean observed prior to 1999. During the 2004 nesting season (study period: 8 June through 22 July 2004), adult kestrels were trapped near the site of their nestboxes. Blood samples were obtained, and serum antibodies specific to WNV were quantified using a plaque reduction neutralization test. Of 22 birds tested, 21 exhibited serum antibodies to WNV, suggesting that most (95%) of the adult kestrels in the population had been exposed to WNV.

DETECTING POPULATION TRENDS IN MIGRATORY BIRDS OF PREY

Abstract Counts of visible migrants at traditional watchsites throughout North America provide an opportunity to augment population-monitoring efforts for birds of prey. We analyzed hourly counts of migrating raptors at one inland (Hawk Mountain Sanctuary, Pennsylvania) and one coastal (Cape May Point, New Jersey) watchsite in northeastern North America. Hourly counts of migrants have been collected for 38 years at Hawk Mountain Sanctuary and for 28 years at Cape May Point. We compared effort-adjusted, arithmetic-mean passage rates to five geometric-mean indexes for 12 species. We used reparameterized polynomial regression to estimate trends in the indexes and to test the significance of trends from 1976–1978 (average index over three-year period) to 2001–2003. Effort-adjusted, arithmetic-mean indexes corresponded to more sophisticated indexes on the complete data sets but did not perform well on simulated data with missing observation days. We recommend the use of a regression-based, date-adjusted index ...

SOARING AND GLIDING FLIGHT OF MIGRATING BROAD-WINGED HAWKS: BEHAVIOR IN THE NEARCTIC AND NEOTROPICS COMPARED

We compared migrating behavior of Broad-winged Hawks (Buteo platypterus) at two sites along their migration corridor: Hawk Mountain Sanctuary in eastern Pennsylvania and the Kéköldi Indigenous Reserve in Limón, Costa Rica. We counted the number of times focal birds intermittently flapped their wings and recorded the general flight type (straight-line soaring and gliding on flexed wings versus circle-soaring on fully extended wings). We used a logistic model to evaluate which conditions were good for soaring by calculating the probability of occurrence or absence of wing flaps. Considering that even intermittent flapping is energetically more expensive than pure soaring and gliding flight, we restricted a second analysis to birds that flapped during observations, and used the number of flaps to evaluate factors influencing the cost of migration. Both the occurrence and extent of flapping were greater in Pennsylvania than in Costa Rica, and during periods of straight-line soaring and gliding flight compared with circle-soaring. At both sites, flapping was more likely during rainy weather and early and late in the day compared with the middle of the day. Birds in Costa Rica flew in larger flocks than those in Pennsylvania, and birds flying in large flocks flapped less than those flying alone or in smaller flocks. In Pennsylvania, but not in Costa Rica, the number of flaps was higher when skies were overcast than when skies were clear or partly cloudy. In Costa Rica, but not in Pennsylvania, flapping decreased as temperature increased. Our results indicate that birds migrating in large flocks do so more efficiently than those flying alone and in smaller flocks, and that overall, soaring conditions are better in Costa Rica than in Pennsylvania. We discuss how differences in instantaneous migration costs at the two sites may shift the species' migration strategy from one of time minimization in Pennsylvania to one of energy minimization in Costa Rica.

TIMING AND MAGNITUDE OF BROAD-WINGED HAWK MIGRATION AT MONTCLAIR HAWK LOOKOUT, NEW JERSEY, AND HAWK MOUNTAIN SANCTUARY, PENNSYLVANIA

The Broad-winged Hawk (Buteo platypterus) breeds in eastern and central Canada and the United States, and winters in Central America and northern and central South America. Birders and ornithologists count migrating Broad-winged Hawks at dozens of traditional watch sites throughout the northeastern United States. We modeled counts of migrating Broad-winged Hawks from two raptor migration watch sites: Montclair Hawk Lookout, New Jersey, and Hawk Mountain Sanctuary, Pennsylvania, to determine whether annual abundance and trend estimates from individual sites within the mid-Atlantic states are representative of the region as a whole. We restricted ourselves to counts made between 10:00 and 16:00 EST during September to standardize count effort between sites. We created one model set for annual counts and another model set for daily counts. When modeling daily counts we incorporated weather and identity of individual observers. Akaike’s Information Criteria were used to select the best model from an initial set of competing models. Annual counts declined at both sites during 1979–1998. Broad-winged Hawk migration began, peaked, and ended later at Montclair than at Hawk Mountain, even though Hawk Mountain is 155 km west-southwest of Montclair. Mean annual counts of hawks at Montclair were more than twice those at Hawk Mountain, but were not correlated. Broad-winged Hawks counted at Montclair may not be the same birds as those counted at Hawk Mountain. Rather, the two sites may be monitoring different regional subpopulations. Broad-winged Hawks counted at the two sites may use different migration tactics, with those counted at Hawk Mountain being more likely to slope soar, and those at Montclair more likely to use thermal soaring. A system of multiple watch sites is needed to monitor various breeding populations of this widely dispersed migrant.

Follow Your Elders: Age-related Differences in the Migration Behavior of Broad-winged Hawks at Hawk Mountain Sanctuary, Pennsylvania

We studied the flocking behavior of adult and juvenile Broad-winged Hawks (Buteo platypterus) migrating past Hawk Mountain Sanctuary in eastern Pennsylvania during September 1996 and 1997. Adults were more likely than juveniles to fly in flocks (78% versus 62%). All-juvenile flocks had a mean of 2.0 (±0.0) birds, all-adult flocks a mean of 4.5 (;pm0.4) birds, and mixed-age flocks had a mean of 4.7 (;pm0.4) birds. Adults, which made up 68% of all individuals in mixed-age flocks, were the first or “lead” birds in 80% of these flocks. Most (58%) adults migrated in the first, or leading, half of such flocks, and most (68%) juveniles migrated in the trailing half. Overall, our results suggest that migrating juvenile Broad-winged Hawks are more likely to follow adults than vice versa. Following experienced adults may help juveniles in two ways, first by allowing them to find thermals more quickly, and second by enabling them to better navigate to appropriate wintering areas.

Long-Term Counts of Migrating Raptors: A Role for Volunteers in Wildlife Research

The science of conservation biology and the practice of wildlife management depend upon long-term databases, but collecting such data can be difficult, expensive, and labor intensive. Conservation biologists and wildlife managers have long used nonprofessional volunteers to collect much of the information needed to make informed decisions concerning the resources they are attempting to understand and protect. The advent of the modern field guide in the 1930s, together with the growing availability of prismatic binoculars, heralded the modern age of recreational bird watching. Since then, bird watchers have made significant and substantial contributions to our understanding of bird populations in North America. Hawk Mountain Sanctuary in eastern Pennsylvania has used volunteer hawk watchers, in conjunction with its own paid staff, to help create the longest and most complete record of raptor migration in the world. The Sanctuary's annual counts of migrating raptors have proved a critical resource in assessing long-term trends of raptor populations in northeastem North America. The extensive database played a key role in exposing the threat of organochlorine pesticides to bald eagles (Haliaeetus leucocephalus) and other predatory birds earlier this century, as well as in tracking more recent recoveries in many of the same populations. Recent analyses of the database are yielding insights into (1) how cold fronts affect counts of raptors at migration watchsites, (2) the extent to which climate change affects the timing of raptor migration, and (3) changes in the migratory habits of sharp-shinned hawks (Accipiter striatus) in eastern North America. I submit that volunteers will play increasingly important roles in wildlife conservation wherever their efforts can be coupled with those of professional practitioners in the field.