During the spring and summer of 2014, with much help from Ken Furrow of Furrow Productions, and numerous landowners, we conducted our ninth survey for Swainson’s Hawks (SWHA) nesting in the Missoula Valley.
Since 2005, we have identified 17 SWHA territories (areas where one or more adults are observed throughout a breed- ing season) in our study area. This year we encountered SWHAs on 7 of these territories, and documented nesting efforts on five. Unfortunately, two of these nests failed, and the three successful nests fledged a total of just five young. This year’s occupancy and productivity rates were similar to 2012 and 2013, but a marked decrease from 2006, when we recorded 17 successful fledglings from a total of ten active nests. This downward trend in occupancy and productivity is troubling, especially when we consider that our knowledge of territories, survey efforts and area covered is greater than ever. We will continue working hard to better understand our Missoula Valley SWHA population, and determine what factors influence nest site selection, productivity, as well as nest failures and abandonment.
We have banded 57 individuals and marked 46 with unique- ly color-coded leg bands. In 2014 we re-sighted one “new”, or previously not re-encountered, color-banded SWHA, bringing our total to 18 re-sightings. This gives us a 39% over- all encounter rate. Colored bands allow us to identify hawks from a distance, and keep tabs on their breeding behavior, survivorship, territoriality, nest site and mate fidelity.
Natal Dispersal Records
To date, we have recorded six natal dispersals. Historically, ornithologists debated whether or not birds return as adults to their natal ground to nest, or simply find suitable areas elsewhere. SWHAs are known to be faithful to their natal grounds and now, through color banding, we are excited to see that behavior in our Missoula Valley population.
Orange w/black zigzag (left leg) was banded at the now defunct Wal-Mart territory in 2006 - the last year the territo- ry was active. This female was re-sighted at the Saunders Territory in 2011 where she and her un-banded mate suc- cessfully fledged one youngster. She has not been seen since.
Blue w/white zigzag (right leg) was banded as a nesting in 2006 at the Moccasin Road nest site, which has not been active since 2007. This male was observed in 2013 with a “metal only” female, who was likely captured before we started using color bands. They nested in a mature Douglas Fir. Unfortunately, shortly after they laid eggs, a new house construction project broke ground directly under their nest tree. The disturbance was more than they could tolerate and they abandoned their nest and young nestlings. In 2014, we were surprised when he and his mate returned to the same nest tree and successfully fledged two young.
Blue w/white zigzag (left leg) was banded in 2006 and sibling to blue w/white zigzag (right leg). We spotted this hawk numerous times near the Valeo Ranch in 2009 and 2010, and though it was definitely holding the territory, we detected no evidence of successful breeding.
Black with white polka dots (left leg) was banded as a nest- ling in 2008 at the Lucier territory. This season, we re-sight- ed him for the first time, with a female that was banded as an adult in late August, 2011 near Frenchtown (green/ yellow (right leg), black/metal (left leg). The pair held the 44 Ranch Territory; even though we observed mating and courtship behaviors throughout the early part of the sea- son, we were unable to confirm nesting. It is possible they nested on Missoula International Airport grounds, which is off limits for surveys.
Green/metal (left), blue/Yellow (right), was banded in 2010 shortly after fledging on the 44 Ranch territory. She was re-sighted on Loiselle Lane territory in 2013. We did not see her with a male and the territory remained vacant. She was observed only once.
Nest mate to the hawk above, blue/metal (left), green/ black (right) was re-sighted on Mullan Road, near French- town in 2014 with an un-banded dark morph female. We have observed SWHA pairs in this area before, but have never been able to locate a nest, or confirm successful breeding.