Notes From the Field: The Rough-legged Hawk Project

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"Notes From the Field” are contributed articles that highlight current banding projects and the continued importance of bird banding 100 years after the establishment of the Bird Banding Lab. Our first article in this new series focuses on a remote-tracking study that examines the movement ecology of Rough-legged Hawks (Buteo lagopus) across North America. 

The side view of an adult male Rough-Legged Hawk showing that he has been outfitted with a GPS-PTT "backpack" transmitter.

Adult male Rough-legged Hawk outfitted with a GeoTrak GPS-PTT transmitter.  (Credit: Neil Paprocki, Idaho Cooperative Fish and Wildlife Research Unit.)

“Notes From the Field” news articles highlight the continued importance of bird banding in celebration of the centennial of the Bird Banding Lab. This article was contributed by Neil Paprocki, whose dissertation research at Idaho’s Cooperative Fish and Wildlife Research Unit involves remote tracking of Rough-legged Hawks (Buteo lagopus) throughout North America.  

Today, banding allows scientists to track birds’ behavior, migration, lifespans, populations, diseases and levels of environmental contaminants. Information gathered through the North American Bird Banding Program helps inform management and conservation decisions of game and non-game species, such as protecting or restoring habitat, setting hunting regulations and determining plans for human development. The North American Bird Banding Program depends on a network of over 10,000 permitted bird banders working in the United States, Canada and Trust Territories. Each year these banders help us add up to 1.2 million new banding records to our century-long dataset.

How do you use bird banding in your research? 

My research is part of a broader study initiated by Jeff Kidd in 2014 to answer questions related to the movement ecology of Rough-legged Hawks. Our project involves capturing and outfitting Rough-legged Hawks with remote-tracking devices throughout North America during all periods of the annual cycle. When we have hawks in hand we also take feather and/or blood samples, and gather morphometric, demographic (age and sex), and plumage. Rough-legged Hawks are one bird species where males and females winter at different latitudes, a phenomenon called differential migration. My dissertation project began in 2019 to help answer the questions, “Why does differential migration occur?” and more specifically, “Why does migration distance vary among individuals?”  

Why is your study species so interesting? 

Past observational work on the wintering grounds has found adult females winter farther north on average than adult males, a pattern exactly opposite than found in most other bird species. This pattern would suggest adult females migrate shorter distances than adult males but why this pattern exists remains unknown. In addition, Rough-legged Hawks exhibit reversed sexual-size dimorphism (females larger than males) as well as plumage dimorphism such that many adult males and females are distinct in their plumage pattern, although much overlap exists. Why Rough-legged Hawks exhibit such plumage dimorphism while other closely-related species apparently do not is still an unanswered question.  

A map of North American showing the year-round GPS movements of 77 individual Rough-Legged Hawks tracked for at least one season

Year-round GPS movements of 77 Rough-legged Hawks tracked over at least one seasonal migration path. (Credit: Neil Paprocki, Idaho Cooperative Fish and Wildlife Research Unit. )

 What have you found so far?  

Since 2014, we have deployed 114 remote-tracking devices on Rough-legged Hawks that have collected over 300,000 GPS or Argos location fixes. We have calculated a suite of descriptive migration statistics (e.g., timing, distance, duration, speed, etc.) that represent the first large-scale tracking of this species in North America. Although I am in the beginning of my dissertation research, our dataset has been incorporated into a larger study about the migration of several raptor species in North American and Eurasia

Why do you think projects like yours are so important? 

My dissertation project will help us understand the mechanisms governing migratory decisions. Remote-tracking Rough-legged Hawks allows us to precisely determine migration distances between summer and winter ranges. Since variation in individual migration distance may be explained by a suite of hypotheses, data derived from remote-tracking birds helps us test explicit predictions associated with these hypotheses. For example, we can determine precise arrival dates to the summer range to test the prediction that hawks with shorter migration distances should arrive to the summer range earlier. By gaining an increased understanding of why birds migrate, we can better predict how migratory systems may change and adapt in response to large-scale environmental change (e.g., climate change). You can learn more about our project and the birds we have marked so far at the Rough-legged Hawk Project Facebook Page

What are the next steps for your project? 

In the short term, we will deploy GPS transmitters on Rough-legged Hawks throughout the Great Plains states during the winter of 2020-2021. This will help broaden the geographic scope of our project as most of our transmitters that are on birds now were deployed west of the Rocky Mountains. We’re looking for additional banders that could help facilitate winter trapping and deployment visits by Neil Paprocki during the next two winters to help extend the reach of our study. Interested banders should contact Neil Paprocki at neilpaprocki@gmail.com.  

The “Notes From the Field” series highlights current banding projects and the continued importance of bird banding 100 years after the establishment of the Bird Banding Lab. Want to see your project featured in a future “Notes From the Field” article? Email Jenn Malpass at jmalpass@usgs.gov for submission details. 

A researcher spreads the right wing of an adult female Rough-Legged Hawk to examine her plumage

An adult female Rough-Legged Hawk. (Credit: Neil Paprocki, Idaho Cooperative Fish and Wildlife Research Unit.)