OLOG ITH ICA N L R SO O C S I A E X T E Y T BULLETIN OF THE TEXAS ORNITHOLOGICAL SOCIETY Vol. 47 No. 1–2 December 2014 Published by the Texas Ornithological Society www.texasbirds.org THE TEXAS ORNITHOLOGICAL SOCIETY OFFICERS JIM HAILEY BRYON STONE SHELIA HARGIS PRESIDENT PRESIDENT-ELECT VICE-PRESIDENT DAVID SARKOZI SANDI WHEELER STEVE GROSS SECRETARY TREASURER PAST-PRESIDENT JACK EITNIEAR EDITOR MEMBERSHIP Any person interested in the birds of Texas may become a member of the Texas Ornithological Society. Individual membership rates are $25.00 per year, $50.00 at the Sustaining level, $15.00 Student, Family $35.00, $400.00 Life and $500.00 Life w/Spouse. These memberships include print versions of Texas Birds Annual, The Bulletin of the Texas Ornithological Society and the electronic version of TOS NEWS. To become a member send check or money order in U.S. funds with complete name and address to: Texas Ornithological Society Memberships, PMB #189, 12468 Austin Highway, San Antonio, Texas 78209. Memberships can also be obtained by consulting www.Texasbirds.org PUBLICATIONS The Bulletin of the Texas Ornithological Society is an annual1 journal devoted to the biology and conservation of the birds that occur in Texas and adjacent areas. Texas Birds Annual is published each year and includes new birding areas, recent media, vagrants and noteworthy birds from the previous year, articles on bird conservation issues and species profiles. TOS News is a tri-annual electronic newsletter produced by TOS. Two issues include registration information on TOS meetings and a third includes information promoting membership in the society. A hardcopy version is available on request. Occasional Publication Series is published on an irregular basis on scientific works too long for publication in the Bulletin. When published it is provided free to all members as an extra benefit of membership during the year of publication. Submission to all publications should be e-mailed to: [email protected] Changes of address and queries about memberships or missing copies: E-mail TOSmember@ yahoo.com or submit in writing to the address above. PERMISSION TO COPY The Texas Ornithological Society hereby grants permission to copy articles (in whole or in part) appearing in The Bulletin of the Texas Ornithological Society (Bulletin) and Texas Birds Annual (TBA) for personal use, or educational and/or personal use, without payment, provided the material reproduced includes the statement “©2011 The Texas Ornithological Society” and contains the full citation, including names of all authors. TOS does not maintain copyright for photographic material therefore does not allow any reproduction of such material without written consent of the photographer. Any use not specifically granted here, and any use of Bulletin or TBA articles or portions thereof for advertising, republication, or commercial uses, requires prior approval from the Editor ([email protected]). 1Starting with Vol. 42 both issues were combined. Cover photo: Adult male Broad-billed Hummingbird. Photo by Maryann Eastman. Frontispiece. American Oystercatcher (Haematopus palliatus). Art compliments of Alexandra E. Munters. BULLETIN OF THE TEXAS ORNITHOLOGICAL SOCIETY TESTING FIELD SEXING TECHNIQUES FOR AMERICAN OYSTERCATCHERS Alexandra E. Munters1,3, Susan A. Heath2 and M. Clay Green1 1Wildlife Ecology Program, Department of Biology, Texas State University, San Marcos, TX 78666, USA 2Gulf Coast Bird Observatory, Lake Jackson, TX 77566, USA ABSTRACT.—Distinguishing the sexes of adult American Oystercatchers in the field is challenging because this species is plumage monomorphic and there is considerable overlap between the sexes in morphometric measurements. We attempted to shed light on this challenge by examining a trait that American Oystercatchers share with other oystercatcher species; the presence of iridial depigmentation, or darkened regions within the yellow iris, known as eye flecks. We used morphometric measurements coupled with the presence and severity of eye flecks to sex pairs of adult oystercatchers, captured as part of a larger study addressing the species’ breeding ecology in Texas. We collected whole blood for genetic determination of sex using polymerase chain reaction (PCR) amplification of the chromo-helicase-DNA binding protein (CHD) gene on avian sex chromosomes Z and W to confirm the reliability of morphometrics and amount of eye flecks as diagnostic tools in our assignment of sex. We captured and sexed molecularly a total of 42 adult oystercatchers and were able to assign sex in the field to 34 of the birds captured. Lab results confirmed that our assessments were 97% correct (33 out of 34) for the birds whose sex we were able to determine in the field. For oystercatchers captured in Texas, there was a significant difference between the sexes for all morphometric measurements and amount of eye flecks. Although the origin of eye flecks remains unclear, we conclude that they can be used to assist in reliably sexing adult American Oystercatchers. For species of conservation concern, life history species that have experienced population declines, details such as differences between the sexes and are now listed as a Species of High Concern in resource partitioning to chicks, site fidelity, in the United States Shorebird Conservation Plan survivorship, and dispersion, are crucial to creating (Brown et al. 2001). This species demonstrates appropriate recovery plans (Clutton-Brock 1986; a life history of paired territorial partnerships in Ellegren and Sheldon 1997). However, many which both sexes share incubation and chick rearing shorebirds of the order Charadriiformes are not duties. Reliably differentiating the sexes of a pair of sexually dimorphic and therefore difficult to sex in territorial oystercatchers without having to collect the field. American Oystercatchers (Haematopus blood and molecularly sex the birds in the lab would palliatus) are a plumage monomorphic shorebird be useful for conservation biologists monitoring this 1Email: [email protected] 3Current Address: 9400 Old Mount Vernon Road, Alexandria, VA 22309 Bull. Texas Ornith. Soc. 47(1-2): 2014 2 species and studying their territoriality, foraging METHODS behavior, and reproductive success. We monitored breeding pairs of oystercatchers on Although American Oystercatchers are plumage the upper Texas coast (29° 29' N, 94° 93' W) from monomorphic, adult females are generally bigger February through July, 2011 and 2012. We captured and heavier than adult males (Carlson-Bremer et males and females with whoosh nets, decoy-noose al. 2010). However, in Virginia, South Carolina, traps, and box traps on their territory or at their nest and Georgia, there was considerable overlap in (McGowan and Simons 2005). We limited whoosh weight, bill length, and wing length between males netting attempts to less than one hour whenever and females (Carlson-Bremer et al. 2010). This possible to minimize disturbance. morphometric overlap can make distinguishing the Once captured, we banded individuals with U.S. sex of an adult oystercatcher challenging if only one Geological Survey Bird Banding Lab stainless steel member of the pair is captured. Another method of bands and color-coded darvic bands for individual sexing adults is checking for cloacal distension identification in the field. Identification leg bands immediately following egg-laying. However, this were placed on each bird in accordance with method is only useful if the female is trapped American Oystercatcher Working Group protocols immediately after she has laid eggs. for permanent identification. We recorded the wing We attempted to shed light on the potential chord, culmen length, tarsus length and mass of difficulty of sexing adult oystercatchers in the captured individuals; all linear measurements were field by examining a physical characteristic of made using standard calipers and wing rules and American Oystercatchers that they share with other mass was measured with a 1,000 g Pesola spring oystercatcher species. A number of oystercatcher scale. We recorded presence and severity of eye species show the presence of iridial depigmentation, flecks (none, minimal, moderate, severe) and took or darkened regions within the yellow iris, henceforth photographs of the eyes of individuals for further termed “eye flecks.” In Black Oystercatchers a posteriori classification. Based on morphometric (Haematopus bachmani), Guzzetti et al. (2008) measurements and the severity of eye flecks, we found the presence of eye flecks in their irises to assigned sex to both members of captured territorial be a predictor of sex in adult females. Researchers pairs, with the female as the larger bird with more used categories of low, medium, and high eye flecks eye flecks. When only one member of a breeding to classify captured birds in the field. Guzzetti et pair was captured, we used morphometrics and the al. (2008) found that for Black Oystercatchers, presence and severity of eye flecks to determine sex. researchers more frequently correctly identified If the amount of eye flecking was indeterminate and sex using eye flecks as a diagnostic tool rather the measurements fell in the overlap zone between than discriminant analysis based on morphological males and females, we recorded sex as unknown. characteristics. Similarly, Kohler et al. (2009) found When birds were captured, a maximum of 1 ml of that eye flecks can serve as a reliable indicator of blood was collected by venipuncture