Northern goshawk breeding ecology and nestling growth in mixed coniferous forests of west-central Idaho

• Main Authors: Hanauska-Brown , Lauri A., Bechard, Marc J., Roloff, Gary J.
• Format: Text
• Language: English
• Published: WSU Press 2003
• Subjects: habitat quality; mixed coniferous-forests; nestling chronology; nestling growth; productivity; Northern Goshawk
• Online Access: http://hdl.handle.net/2376/1027

This study documented the nesting chronology, productivity, and nestling growth of northern goshawks in west-central Idaho in 1998 and 1999. Egg laying began in late April, and fledging occurred in mid-July. Goshawks used >35% of historical territories and eleven new territories were discovered. Of 46 occupied territories, 80% were successful, fledging one to four young. Productivity averaged 2.1 fledglings/successful nest in 1998 and 2.0 fledglings/successful nest in 1999. Failure rates were similar between years; 17% of occupied territories failed in 1998 and 21% failed in 1999. We also measured nestling growth, a variable not previously reported for goshawks in any northwestern studies. Time for nestlings to grow from 10 to 90% of their fledging mass ranged from 16 to 35 days and their growth-rate constants, k, ranged from 0.13 to 0.27. Nestling growth rates were similar within nests, but varied among nests. The fastest mean growth at a nest was 17 days to reach 90% of fledging mass, while the slowest mean growth was 33 days to reach 90% of fledging mass. Variability in growth among nests suggested there were differences in energy intake by nestlings, potentially due to adult condition or habitat quality. Nestling growth may be a valuable indicator of habitat quality and adult breeding condition during the nestling stage. In contrast, productivity (as defined in this study) can be viewed as a more encompassing expression of habitat quality including quality of the adult winter range and breeding habitat HanauskaBrown et al "Northern goshawk breeding ecology and nestling growth in mixed coniferous forests of west-central Idaho." Northwest Science. 2003; 77(4): 331-339