Birder's Guide

NOV 2013

Birder's Guide is the American Birding Association's newest publication. Each issue focuses on a key subject, providing tips from experienced birders on a wide variety of topics like Travel, Listing & Taxonomy, Gear, and Conservation & Community.

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Page 40 of 67

200 kilometers from the source. A statesponsored eradication program resulted in the shooting of 3,187 swamphens between October 2006 and December 2008, before the program was deemed a failure and discontinued. Based on specimen and DNA evidence, the Purple Swamphens in Florida represent the gray-headed subspecies poliocephalus, which is native from the Caspian Sea and Iraq to Indochina and Sumatra. Sangster (1998) considers poliocephalus to represent a separate species, which he calls Gray-headed Swamphen. A thorough overview of the natural history of Purple Swamphens in Florida is provided by Pranty (2013), and a basic sketch is given by Pranty et al. (2013). Comments The history of exotics added to the ABA Checklist shows a maturing attitude from the CLC, as well as the chaotic status of the introduced populations. The frst Checklist (Robbins et al. 1975) contained 16 species considered exotic: Cattle Egret (!), Mute Swan, Ring-necked Pheasant, Chukar, Gray Partridge, Black Francolin, Rock Pigeon, Spotted Dove, African Collared- Dove (then called Ringed Turtle-Dove), Red-whiskered Bulbul, European Starling, Crested Myna, Blue-gray Tanager, Spot-breasted Oriole, House Sparrow, and Eurasian Tree Sparrow. The 1975 Checklist required that two criteria be met before an exotic was considered by the CLC to be established: (1) breeding for 10 years and (2) a stable or increasing population (Robbins et al. 1975). Although we intend no criticism of the pioneering work of the CLC in its earliest years, we have come to realize that the 1975 Checklist employed limited and short-term criteria that were insuffcient for determining the successful establishment of exotic bird populations. By the seventh ABA Checklist (Pranty et al. 2008), the number of exotics had increased to 18, with eight additions (Himalayan Snowcock, Eurasian CollaredDove, Budgerigar, Monk Parakeet, Green Parakeet, White-winged Parakeet, Redcrowned Parrot, and Common Myna) and six deletions. Of the deletions, two species had been reclassifed (the Cattle Egret as a natural colonizer and the European Starling as a natural vagrant/established exotic), and four others had been removed because their populations had become extirpated: Black Francolin (removed in 1990), African Collared-Dove (1994), Crested Myna (2004), and Blue-gray Tanager (1982). By 2008, the CLC had expanded the number of criteria required to meet the CLC's defnition of an established exotic to eight, including a more rigorous temporal criterion. These eight criteria are discussed in detail in Pranty et al. (2008) and are available online . Note that even meeting all eight of these criteria is not necessarily suffcient for adding a species to the ABA Checklist. For example, in 2006 the CLC rejected the establishment of Nanday Parakeet in westcentral Florida despite its meeting all eight CLC criteria, because two members were concerned that the occupied range was too small (Pranty et al. 2006). On the basis of updated information on population size and range expansion, the CLC added Nanday Parakeet to the ABA Checklist six years later (Dunn et al. 2012). During the past 25 years, 10 species of exotic birds have been added to the ABA Checklist. One of these species, Yellowchevroned Parakeet, was removed after Florida's Purple Swamphens are of the gray-headed subspecies poliocephalus, as is this individual in Thailand. Photo © Bob Steele. November 2013 | Birder's Guide to Listing & Taxonomy 39

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