by Jesse Watson and Jay Winiarski
Visit the Full Cycle Phenology website to read their latset blog post and learn more about the project.
In 2014 we initiated our American Kestrel Study along the Wasatch Front to address concerns about reported population declines over the past few decades. In addition to investigating and addressing these concerns at a local level, HawkWatch also contributes data to the American Kestrel Partnership, who help coordinate Kestrel nestbox monitoring efforts across North and South America to advance Kestrel conservation on the continental scale.
Figure 1 Male American Kestrel prior to release after feather sampling, New Mexico
As the climate changes and shifts in seasonal timing are documented, animals may alter behavior and the timing of life cycle events such as the initiation of breeding, migration departure dates, or the distance of migration. Such changes in phenology may have serious impacts on breeding success and species survival, which may have important consequences for specific populations or the status of an entire species. Furthermore, because much of our current knowledge about raptor populations is limited to long-term migration counts, important details such as: if, when, and how far they migrate are currently unknown. The Full Cycle Phenology Project (FCP), is a focused effort studying the American Kestrel, whose widespread breeding distribution and highly variable migration strategies, presents a model system for climate change research. The project employs cutting edge genetic techniques and large-scale collaboration among citizen and professional scientists across North America to study Kestrel phenology. The project is supported by the Strategic Environmental Research and Development Program of the Department of Defense and creates one of the largest networks for monitoring full annual cycle phenology of a migratory land bird.
Figure 2 Female American Kestrel, Florida
As part of this effort, HawkWatch International is working with Boise State University, University of California, Los Angeles, St. Mary’s University, the American Kestrel Partnership, and the Environmental Laboratory of the U.S. Army Engineer Research and Development Center to study Kestrels during summer, fall, winter, and spring, across their North American range to determine how migration strategies (distance and destination) differ based on environmental and genetic factors. Variation in migration among North American Kestrels can be compared across the annual cycles to determine changes in phenology.
Figure 3 Removing a feather from a Female American Kestrel to obtain a genetic sample
In mid-February we wrapped up winter season data collection, a focused effort to collect genetic samples (from feathers) from wintering Kestrels from across their range within the USA. Scientists from HawkWatch International and Boise State University’s Global Change Ecology lab sampled 191 individuals across 15 states from mid-November through mid-February! These genetic samples will provide insight into where wintering individuals migrated from and where they may breed by determining where their genetic signature falls on the Kestrel genoscape map. The development of the American Kestrel genoscape is an ongoing process and as we continue to collect and analyze genetic samples, we hope to gain more resolution with the genetic signatures of distinct genetic groups becoming more refined.
The high resolution genetic methods we are using to determine migratory connectivity are new, and we don’t yet know how strongly genetic signatures differ between groups. Hence, to validate results of our genetic methods, we are deploying GPS satellite transmitters on a subset of wintering Kestrels to determine exactly where they migrate and breed.
Figure 4 Female American Kestrel with GPS Satellite transmitter, southern Texas
Additionally, satellite tracking will help us understand how environmental variation experienced across the species’ range and annual cycle impact the timing of departure/arrival, migration speed and length, and subsequent seasonal events. For example, climatic conditions Kestrels face on their wintering grounds could affect the timing and duration of spring migration, which in turn could influence when Kestrels breed and their reproductive success. With the connectivity and timing information provided by these technological advances, we can begin to better understand how Kestrels are responding to climate change today and in the future.
Figure 5 Female American Kestrel wearing GPS satellite transmitter
Although GPS satellite telemetry technology is always improving, the slow miniaturization of tags available to researchers limits telemetry research on small raptors and other birds. Until recently, the three factors restricting the use of such transmitters on Kestrel-sized birds included: weight; battery life (both of which are correlated); and the need to recapture individuals to remove the tag/collect the data. After much discussion and brainstorming with wildlife monitoring companies we chose a transmitter that is light enough for Kestrels, can last through multiple seasonal cycles (winter, spring, summer), and does not need to be recovered to retrieve the data (it transmits remotely)! We deployed the first of these transmitters in January on three female Kestrels in southern Texas. So far, none of the individuals have migrated north from the areas where they were captured but we are anxiously waiting to see where they migrate and potentially breed!
Figure 6 Telemetry locations for one female Kestrel in southern Texas (locations collected mid-January through February).