Alula Characteristics As Indicators of Golden-Cheeked Warbler Age

Alula Characteristics as Indicators of Golden-cheeked Warbler Age

Rebecca G. Peak and Daniel J. Lusk (SY) birds from older age classes. Dwight (1900) P.O. Box 5190 first illustrated the utility of molt limits in ageing Fort Hood, TX 76544 passerines. More recent literature on the use of molt [email protected] limits to age North American passerines provide detailed descriptions ofhow to distinguish different feather generations from each other for a variety of ABSTRACT species (Yunick 1984, Pyle et al. 1987, Mulvihill 1993, Pyle 1997a, Pyle 1997b ). We assessed the alula ofGolden-cheeked Warblers (Dendroica chrysoparia) to determine its usefulness Dendroica warblers retain greater primary coverts as a criterion for age determination. We compared (hereafter "primary coverts") from the juvenal the alula to the greater secondary coverts for color plumage but replace greater secondary coverts contrast and examined it for presence of white. (hereafter "greater coverts") during the first Overall, 98.2% ofsecond-year birds had an alula/ prebasic molt (Pyle et al. 1987). Hence, greater secondary covert contrast; whereas, I 00% comparison of color and extent of wear between of after-second-year birds did not have a contrast these feather groups is useful for ageing members between these feather groups. All after-second of this genus. The contrast between primary and year birds had white on the alula. Our data greater coverts can be challenging for inexperi demonstrate that these characteristics are reliable enced banders to recognize. These feather groups indicators of age for Golden-cheeked Warblers. are small, the color difference is often difficult for Still, we advocate using them in combination with the untrained eye to discern, and some of these existing ageing criteria to enhance the confidence species replace the inner greater coverts during of banders' age determinations, especially during prealternate molts. the winter and spring when degree of skull pneumaticization is no longer a reliable indicator Pyle (1997a and 1997b) states the first pre basic of age. molt of Dendroica warblers often includes the alula. However, while examining the primary and INTRODUCTION greater coverts of Golden-cheeked Warblers for color and extent of wear, we have observed that the Banders use a variety of techniques for ageing primary coverts as well as the alula of SY birds are passerines. While degree of skull pneumaticization retained feathers from the juvenal plumage. In fact, is recognized as the most reliable ageing technique while training inexperienced banders we have for this group of birds, the skull of most species observed that they often recognize the color becomes fully pneumaticized and is no longer a contrast between the alula and greater coverts more reliable indicator of age at some time during the readily than the contrast in color between primary year (Pyle et al. 1987). Plumage-related criteria also and greater coverts. Furthermore, we have provide banders with useful information for ageing observed that in addition to the lack of contrast in passerines. For example, molt limits, the contrast color with the greater coverts of after-second-year between different feather generations, produce age (ASY) birds, a variable amount of white is present specific plumage patterns that allow banders to on the replaced alula, similar to the description distinguish hatching-year (HY) and second-year given in Pyle (1997a) for variation in the amount of

Page 106 North American Bird Bander Vol. 34 No.3 white in rectrices of Dendroica warblers among Table 1. Characteristics of alula quills of SY and ASY different age and sex classes. The objective of this Golden-cheeked Warblers indicating contrast in color study was to assess the usefulness of these alula be~en alula quills (At, A2, and A3) and greater coverts characteristics in determining age of Golden (gr cov) and presence of mute. cheeked Warblers. SY ASY

METHODS Characteristic AI A2 A3 AI A2 A3 Alula/gr cov contrast We used recorded vocalizations of Golden cheeked Warblers to capture them in mist nets on Present 16 56 55 0 0 0 Fort Hood Military Reservation in central Texas Not Present 34 I 2 33 36 36 between March and June 2009. See Eckrich et al. Data Not Recorded I 0 0 1 I 1 (1999) for detailed descriptions of the Fort Hood site. After capture, we banded individuals with a White U.S. Geological Survey aluminum band and a Present 1 0 2 19 34 34 unique combination of color bands and used criteria Not Present 41 48 45 14 1 1 described in Pyle (1997a) to age and sex them. We examined the alula for retainedjuvenal plumage by Data Not Recorded 9 9 10 1 2 2 comparing its color with that of the replaced greater Quill Not L

RESULTS DISCUSSION

We examined 94 Golden-cheeked Warblers. We found that presence of a color contrast between Seventy-four (78.7%) were males and 20 (21.3%) retained alula and replaced greater coverts as well were females. Twenty-five males and I2 females as presence of white on the alula can be used (39.4%) were aged as ASY birds. Forty-nine males reliably to age Golden-cheeked Warblers ifbanders and eight females (60.6%) were aged as SY birds. only examine A2 and A3. Banders had difficulty We did not detect any difference in either presence locating A 1, possibly because it is a much smaller of retained alula or white on the alula between and more difficult quill to locate than the other two sexes, so we examined data by age classes only quills. When banders were able to locate A I, it did (Table 1). Sometimes, we failed to record alula data not follow the same pattern that A2 and A3 did for or were not able to locate a quill. We excluded these these ageing criteria. Approximately 60% of SY data from the analysis. Overall, 98.2% of the 57 SY birds exhibited symmetric replacement of AI birds had alula retained from the juvenal plumage. indicating that it is molted independently of A2 and However, the percentage varied by quill; 96.5% of A3 during the first prebasic molt, first prealternate A3, 98.5% of A2, and 32.0% of AI quills were molt, or both molts. Jul.- Sep. 2009 North American Bird Bander Page 107 These findings meet the Bird Banding Laboratory's LITERATURE CITED policy that age and sex criteria are at least 95% reliable to be recommended for use in determining Dwight, J., Jr. 1900. The sequence of plumages and age and sex ofbirds. Still, we advocate using these moults of the passerine birds of New York. criteria in combination with existing ageing criteria Annals ofthe New York Academy ofScience 13: to enhance the confidence of a bander's age 73-360. Eckrich, G. H., T. E. Koloszar, and M. D. Goering. determination, especially during the winter and 1999. Effective landscape management of spring when degree of skull pneumaticization is no Brown-headed Cowbirds at Fort Hood, TX. longer a reliable indicator of age. We encourage Studies in Avian Biology 18:267-274. banders to examine other Dendroica warblers, Mengel, R. M. 1964. The probable history of species especially other members of the Dendroica virens formation in some northern wood warblers superspecies complex (Golden-cheeked, Black (Parulidae ). Living Bird 3:9-43. throated Green [Dendroica virens ], Hermit Mulvihill, R. S. 1993. Using wing molt to age [Dendroica occidentalis], Townsend's [Dendroica passerines. North American Bird Bander 18: 1- townsendi], and Black-throated Gray [Dendroica 10. nigrescens] warblers; Mengel 1964 ), for presence Pyle, P. 1997a. Identification guide to North American birds, Part I. Slate Creek Press, Bolinas, CA. ofthese ageing criteria. Pyle, P. 1997b. Molt limits in North American ACKNOWLEDGMENTS passerines. North American Bird Bander 22: 49-90. We thank numerous seasonal field biologists for Pyle, P., S. N. G. Howell, R. P. Yunick, and D. F. field assistance. This project was sponsored in part DeSante. 1987. Identification guide to North American passerines. Slate Creek Press, by the Department of the Army with The Nature Bolinas, CA. Conservancy through Cooperative Agreement Van Tyne, J. and Berger A. J. 1971. Fundamentals of DPW-ENV-07-A-0001. The content ofthis paper ornithology. John Wiley and Sons, NY. does not necessarily reflect the position or policy of Yunick, R. P. 1984. Toward more effective age the Government and no official endorsement determination of banded birds. North American should be inferred. Bird Bander 9:2-4. News Notes Comments History of Computerization of Biological Survey from the Department of Bird-Banding Records: An Addendum Agriculture to the Department oflnterior took place on the 1 Jul1939 (Bird-Banding Notes 2, # 17, Since the publication of Houston, Robbins, and October 1939), because that was the beginning of Klimkiewicz, "History of computerization of bird the new government fiscal year. band.lng :r.ecx:nds," (North American Bird Bander Then, for a few years in the early 1950s, the 33:53-65, April-June 2008), four omitted or banding year was changed to end on 30 Apr. This inadequately explained items have come to our was done to ensure that waterfowl bandings were attention. submitted in time for use in setting that year's hunting season. 1. Calendar years Finally, the banding year moved to the During the 1920s, the banding calendar year standard or normal calendar year through ended30 Jun(e.g.,BirdBandingNotes 1,#13,Nov imposition of a one-time truncated eight-month 1924 and Bird Banding Notes 1, #28, September year, 1 May to 31 Dec 1955. That year, an undated 1929). ThtJS, 1 .J ul was the first day of each banding and untitled 15-page mimeographed document was calendar year. 1 Ven the transfer of the Bureau of sent from the Bird Banding Laboratory (BBL) to Page 108 North American Bird Bander Vol. 34 No. 3