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1 June 2016 Using Banding and Encounter Data to Investigate Movements of Red-Tailed Hawks in the Northeastern United States
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Abstract

We examined encounter records from 1925 to 2015 for Red-tailed Hawks banded in the northeastern U.S.A. (n = 1002) and characterized movement patterns by evaluating straight-line distances, difference in latitude, and directionality between banding and encounter locations. We define “encounter” as any handling of a live banded bird, any recovery (a banded bird found dead), and any resighting (reading and reporting a band number on a live bird without actually handling the bird). The mean direction of all hawk encounters was to the southwest of banding locations but some hawks ranged widely; encounters occurred in 27 states, including some in the Mississippi flyway, and in four Canadian provinces. Hawks banded as nestlings or as hatch-year birds (younger) were encountered at farther distances and across a wider range of latitudes than hawks banded as after-hatch-year (AHY) or after-second-year (ASY; older). Most encounters were of younger hawks. In mid-century, most known mortalities were due to shooting; more recent mortalities were due to collisions with vehicles, buildings, or other objects. Some young hawks apparently dispersed out of their natal areas or began migration by three mo post-fledging, and hawks hatched in the Northeast apparently do not migrate north during their first summer. Hawks banded at higher latitudes were encountered at locations farther south than hawks banded at lower latitudes, substantiating leapfrog migration in this species. Encounter data suggested philopatric tendencies; hawks banded as nestlings and encountered at >46 mo of age were encountered significantly closer to their natal areas than hawks banded as nestlings and encountered <46 mo after banding, and more than 10% of hawks banded as ASY or AHY were encountered after several years in the same 10-minute block in which they were banded. Hawks banded as nestlings and encountered at age >46 mo and >250 km from their natal area were considered long-distance dispersers. Between 1930 and 2010, for all hawks banded during the breeding season or summer and encountered in autumn or winter, the difference between banding latitude and encounter latitude decreased by about 4°, suggesting migratory short-stopping.

© 2016 The Raptor Research Foundation, Inc.
Joan L. Morrison and Jason M. Baird "Using Banding and Encounter Data to Investigate Movements of Red-Tailed Hawks in the Northeastern United States," Journal of Raptor Research 50(2), (1 June 2016). https://doi.org/10.3356/rapt-50-02-161-175.1
Received: 4 February 2015; Accepted: 1 December 2015; Published: 1 June 2016
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