Data from: Molt and body measurements for Gray Hawks in the Lower Rio Grande Valley of Texas

We captured 235 Gray Hawks (Buteo plagiatus) in the Lower Rio Grande
Valley (Hidalgo, Willacy, and Cameron counties) of Texas from 6 February
2003 to 8 April 2023. We identified birds in five molt cycles: 115 birds
in their first cycle, 16 in their second cycle, 73 in at least their
second cycle, 19 in at least their third cycle, and 12 in at least their
fourth cycle. Of these, we documented 15 instances of preformative molt,
six instances where birds had an incomplete second prebasic molt,
resulting in one to three retained juvenile rump feathers and/or wing
coverts, and 18 instances where incomplete prebasic molts resulted in
birds with multiple generations of flight feathers. We also present
morphometric data from 144 Gray Hawks (nestlings and first-cycle birds
captured prior to 1 October excluded). These results from the Lower Rio
Grande Valley, on both molting strategies and measurements, differed in
some respects from other sources based on the entire Gray Hawk population,
most notably that birds from this northern and non-migratory population
may show lower incidence of Stafflemauser molting patterns, and that they
are heavier, which supports Bergmann’s rule.