Addressing ferruginous hawk research gaps in the Morley Nelson Snake River Birds of Prey NCA
By Annabel Christiansen
I recently had the opportunity to head out in the NCA to observe the work taking place as a part of the ferruginous hawk project that the Birds of Prey NCA Partnership and the Bureau of Land Management have been collaborating on.
What is a ferruginous hawk?
The ferruginous hawk, Buteo regalis, is among the largest and heaviest of the 27 Buteo hawk species. They thrive in grasslands and open-country,including dry prairie and sagebrush-steppe ecosystems, which makes the NCA the perfect habitat. Because they are incredibly sensitive to environmental factors associated with climate change, as well as human disruption, they can act as an ‘indicator species’ for overall ecosystem health.
Within the state of Idaho, ferruginous hawks are listed as a Species of Greatest Conservation Need, and are a BLM Type 2 Sensitive Species. Their decline in our state can be attributed to the loss of suitable habitat (caused by invasive grasses and human development) and increased fire frequency.
What is this project all about?
The ferruginous hawk project aims to address existing research gaps regarding the distribution, demography and, most importantly, their reproductive performance within the NCA. Along with Steve Alsup, BOP’s President, we were joined by Joe, the resident NCA biologist for BLM as well as Andrew, a fellow BOP intern, and Libby, a prospective PhD student from Colorado State interested in ferruginous hawk (FIHA) research. The FIHA Project aims to answer three key questions regarding the ferruginous hawk population in the NCA:
- How many territories are occupied?
- How many pairs of breeding hawks are within said occupied territories? - Of those pairs, how many are successful? (See notes on what ‘success’ means below).
What would success look like?
‘Success’ is a broad term - BOPP and BLM track success by judging reproductive performance and productivity. This includes how many young are successfully raised from chick to fledgling, how many chicks are in a single nest, and how successful the fledglings are as young adults in the wild.
A large percentage of young fledglings do not survive long after leaving the nest due to predation, difficulty hunting on their own, and other natural factors. With all of this in mind, measuring success can be tricky - which is why this research is so important and why constant monitoring is required.
How large is the NCA’s ferruginous hawk population?
Within the NCA, there are about 60 territories where ferruginous hawks are known to nest, and roughly 20 of them are occupied and considered “active” each breeding season. Within these territories, nesting platforms have been constructed to assist the hawks in providing habitation, giving them a safe space to nest - high above potential ground predators such as foxes, bobcats, and coyotes.
Observation of these platforms began in 2021. On our recent visit we spent the day visiting some of them, checking for chicks, and then banding them. We also collected health and wellbeing data. Out of the 5 platforms we visited, only 1 had chicks at the perfect age to band, which is usually just before they fledge the nest at 38 to 50 days old. We collected and banded 4 chicks, and gathered developmental data, such as weight, leg, bill and talon measurements. From this information, we were able to estimate the ages of the chicks.
Annabel’s reflections
It was an amazing experience being able to witness the ferruginous hawk project in action - these birds are an important part of the ecosystem within the NCA, and it was great to see them well and thriving. The team was so knowledgeable, and it was a treat to work with them for the day and see some cute ferug babies!
