NEWS AND NOTES by Paul Hess
• Rock Dove (Columba livia) becomes Rock Pigeon, to con- form to the recent standard English name change by the British Ornithologists’ Union. Checklistew knowledge, reinterpretation Changes of old ideas, and con- Nservative treatment of uncertainty are central features Reassignments to new genera of the timely (now annual) supplements to the American • Ten species of New World pigeons formerly included in Ornithologists’ Union Check-list of North American Birds. the genus Columba are placed in a separate genus, Pata- The 44th Supplement, published in July 2003 (Auk gioenas, based on genetic, morphological, serological, and 120:923–931), ordains a long list of changes, including behavioral characters that differ from Old World Columba splits of species, new common names and scientific names, species. Four are on the ABA list: Scaly-naped Pigeon (now assignments of species to new genera, rearrangements in P. squamosa), White-crowned Pigeon (P. leucocephala), the linear sequence of taxonomic relationships (colloqui- Red-billed Pigeon (P. flavirostris), and Band-tailed Pigeon ally, the “official checklist order”), and postponement of (P. fasciata). Rock Pigeon, an introduction from the Old other decisions pending the outcomes of further research. World, remains in Columba. Many of the changes involve ABA-area birds, and by stipu- • Ten New World owls of the genus Otus are separated into lation, the AOU classifications and nomenclature are a new genus, Megascops, based on mitochondrial DNA and adopted for the ABA Checklist. The following is a summary vocal differences from Old World Otus owls. Three are of revisions adopted by the AOU Committee on Classifica- ABA-area species: Western Screech-Owl (M. kennicottii), tion and Nomenclature that affect the ABA list. Eastern Screech-Owl (M. asio), and Whiskered Screech- Owl (M. trichopsis). Another North American species, Species splits Flammulated Owl, retains the name Otus flammeolus • New World and Old World populations of Three-toed because of its vocal similarity with Old World Otus species. Woodpecker are separated on the basis of differences in • Snowy Owl, formerly Nyctea scandiaca, becomes Bubo mitochondrial DNA and vocalizations. The North American scandiacus by a merger of its monotypic genus into the species is named American Three-toed Woodpecker, genus Bubo. New studies indicate that Snowy Owl not only Picoides dorsalis, and the Eurasian species retains the name is closely related to Bubo but in fact is genetically “nested P. tridactylus. • A White-winged Crossbill population limited to the island of Hispaniola in the Greater Antilles is split from the North American form, based on vocal and morphological differences. The new species is named Hispaniolan Cross- bill, Loxia megaplaga, and North America’s species retains the name White-winged Crossbill, Loxia leucoptera. Note that the Old World three-toed woodpecker and the crossbill on Hispaniola have not been recorded in the ABA Area, with the result that neither split adds a new species to the ABA list.
New English names • Band-tailed Gull (Larus belcheri), added to the ABA list in 2002 under that name (see Birding 35:138–144), is now Belcher’s Gull, named in parallel to its sister species, Olrog’s Gull.
It’s going to require some getting used to, but Columba livia is no longer the Rock Dove. Instead, it now goes by the name of Rock Pigeon—by authority of the recently published 44th supplement to the AOU Check-list. Oil painting by © Ray Nelson.
22 BIRDING • FEBRUARY 2004 Thraupidae and Fringillidae, and perhaps in the Emberizidae (sparrows) and Parulidae (wood war- blers). For now, asterisks mark 80 such species with uncertain relationships, including 17 on the ABA list: Yellow-breasted Chat, Bananaquit, five tanagers, Western Spindalis, White-collared Seedeater, two grassquits, four longspurs, and Snow and McKay’s Buntings. The committee said that when additional studies resolve the relation- ship of these problematic taxa, formal changes will Long-distance neotropical migrants like the American Redstart (shown here) may have evolved so as be proposed and acted on. to arrive on their breeding grounds at or near the peak of prey availability. However, prey availability (in the form of caterpillars) appears to be have been advancing earlier in the year, presumably as a result of climate change. It is unclear whether migratory species will be able to adapt to shifting Looking ahead patterns of resource availability. Houston County, Minnesota; May 2002. © Stan Tekiela. Among taxonomic proposals the committee con- sidered but has not yet accepted are a merger of the within” this genus. The only other North American species genus Ciccaba (including the ABA-listed Mottled Owl) into in Bubo is Great Horned Owl (B. virginianus). the owl genus Strix and a split of the Seaside Sparrow into two or more species. The committee concluded, “We are Grammatical changes in Latin suffixes aware of reports in our area of several species not now on • Whiskered Tern from Chlidonias hybridus to C. hybrida. our list, but are awaiting consideration of these reports by • Black-capped Vireo from Vireo atricapillus to V. atri- our sister committee of the American Birding Association.” capilla. The updated AOU Check-list is available online at • Black-capped Chickadee from Poecile atricapilla to P. atr-
WWW.AMERICANBIRDING.ORG 23 NEWS AND NOTES
wide regional warming, because the spring temperature pattern has alternated oppositely in northern and southern areas of Strode’s hypothesized migration route. In the four northern states, a warming trend toward earlier springs has Blue Grosbeak advanced the temperature threshold of peak caterpillar abundance as much as 8.9 days earlier from 1912 to 2001. Matearwin’s commentChoice in The Descent of Man, and Selection To the south, along the migration route through Illinois, a Din Relation to Sex sounds quaint now: “On the whole, significant cooling trend has pushed the threshold as much birds appear to be the most aesthetic of all animals, except- as 11.2 days later during the same period. ing of course man, and they have nearly the same taste for Despite the temperature trend toward earlier springs on the beautiful as we have.” Whether for beauty or more the northern breeding grounds, seven of the eight warblers likely for other reasons, female birds of many species have have shown no corresponding trend toward earlier arrival. been shown to prefer brightly colored over duller males for The exception is the Yellow-rumped Warbler, which has mates. To test the role of male Blue Grosbeaks’ plumage been arriving earlier, presumably in response to earlier brightness in females’ mate choice, Barbara Ballentine and springs and, Strode suggested, to early emergence of flying Geoffrey E. Hill devised an experiment using captive birds insects that are this species’ primary prey. Jon L. Dunn and to create a range of plumage variation. As in virtually all Kimball L. Garrett explained in A Field Guide to Warblers of blue birds, the hue in this species is not produced by color North America that the Yellow-rumped is notable among pigment; it results from differential reflection and scatter- warbler species as a facultative migrant, varying the timing ing of wavelengths of light by microscopic structures in the of its movements in accord with weather and food avail- feathers. The authors manipulated this structural “blue- ability. Meanwhile, despite the cooling trend in southern ness” simply by using a blue marking pen to increase feath- Illinois, six of the eight species have not changed their ers’ brightness on one set of males and a black marking pen arrival timing at the Urbana stopover site. The exceptions to decrease the brightness on another set. Then, in a spe- are the Yellow-rumped Warbler and the Ovenbird, which cially designed outdoor aviary, females were presented with have trended earlier, perhaps surprisingly, in light of the a choice between brighter and duller males. trend toward later springs in that area. Ballentine and Hill reported an unexpected result in Strode describes the migrants as “in a 2003 (Condor 105:593–598). bind”: For optimal prey abundance, if the Females chose males irre- temperature trends continue, birds will need spective of plumage intensity. to arrive increasingly later in their more Of the 11 females tested, six southerly stopover areas but increasingly showed a preference for a earlier on their northern breeding grounds. bright male, but five pre- Unchanged arrival timing could indicate ferred a dull one. Although that the birds’ response to photoperiod as a their sample was small, the migration trigger is not flexible enough to authors suggested that it was adjust to the mixed environmental signals. sufficient to conclude that Whether an uncoupling of migration timing variation in males’ brightness and peak prey abundance would affect other had a negligible effect. neotropical migrants is unclear, but poten- What, then, might be the tially it could add further stress to many criterion for female Blue species that are already at risk from habitat Grosbeaks’ mate choice? Bal- loss and other ecological dangers. lentine and Hill noted that males sang and displayed Surprisingly, mate choice in female Blue Grosbeaks throughout the trials, but may not be not directly dependent upon male plumage those behaviors could not be brightness. There may be an indirect effect, however: It tested in the experiment is possible that territorial competition among males is influenced by plumage brightness, and that females, focusing on plumage. The in turn, choose males on the basis of territory size and authors speculated on quality. Kern County, California; June 2003. © Bob Steele. another, less obvious, possi-
24 BIRDING • FEBRUARY 2004 bility. Previous research has morphological features that shown that in territorial compe- corroborated the previously tition among males, brighter described eastern and west- grosbeaks acquire larger territo- ern groups. The clusters sep- ries with more food resources. A arated the two groups even at female might choose a male by their areas of contact in his superior territory rather than southeastern Arizona and directly by the bright plumage northern Jalisco, according to that enabled him to compete Rojas-Soto. successfully for it. Answers At the same time, his await more work with marking results showed no geographic pens and perhaps with micro- patterns of morphological phones as well. variation within either of the two groups to support recog- nition of any of the seven named subspecies—even when analyzing the same Thrasher characters that had been used originally to define the sub- Curve-billed Thrasher (curvirostre group). El Canelo, Texas; February 2003. © Jim Burns. Taxonomyreast, wing, and tail patterns species. Rojas-Soto viewed Bof the Curve-billed Thrasher the described races as almost (Toxostoma curvirostre) differ certainly arbitrary divisions markedly across the species’ based on single rather than wide range in the southwestern multiple characters. More- states and Mexico. Birds of east- over, he said, the subspecific ern populations—those in variations described previ- extreme southeastern Arizona, ously might not have taken New Mexico, Texas, and the into account temporal varia- interior of Mexico—have well- tions such as molt and defined dark breast spots, white feather wear that arise merely wing bars, and large white spots from the individual’s age and on the tail. Birds in the western- the month in which the spec- most portion of the range— imen was collected. those in central and western Rojas-Soto’s morphological Arizona and along the Pacific Curve-billed Thrasher (palmeri group). Phoenix, Arizona; April 2003. © Jim Burns. findings correspond closely slope of Mexico—are spotted The bird currently known as the Curve-billed Thrasher may, in fact, represent two to the results of a mitochon- indistinctly on the breast, lack separate species. The eastern group (curvirostre) is characterized by well-defined dark drial DNA analysis reported wing bars, and show less-dis- breast spots, white wing bars, and large white spots on the tail; the western group in 2000 by Robert M. Zink (palmeri) is distinguished by indistinct breast-spotting, absence of wing tinct white in the tail. Based on bars, and less-distinct white in the tail. and Rachelle C. Blackwell- those differences, the eastern Rago (Condor 102:881–886). populations have been linked informally as three subspecies Their genetic study separated the same eastern and western in a “curvirostre group” and the western populations as four groups as being “reciprocally monophyletic” (i.e., repre- subspecies in a “palmeri group”. senting mutually exclusive evolutionary ancestries). Zink The two groups should be classified as separate species, and Blackwell-Rago said that such groups, especially when Octavio R. Rojas-Soto suggested in 2003 (Auk corroborated by morphological evidence, should be classi- 120:311–322). In several multivariate analyses that fied as separate phylogenetic species because of their evo- included 12 standard measurements, three coloration char- lutionary independence. acters, and the different breast-spot and tail-spot patterns, Although Rojas-Soto found no geographically patterned he found two large non-overlapping statistical clusters of variation within either of the two groups, he suggested that
WWW.AMERICANBIRDING.ORG 25 NEWS AND NOTES
an endemic race on Tiburón and San Esteban islands in the Gulf of Cali- fornia warrants further study. Sev- eral morphological characters differentiate it from the western group, but he said that no taxo- nomic conclusions can be justified without genetic data about the pop- ADVERTISEMENT ulation. Using phylogenetic analy- ses, Zink and Blackwell-Rago also found no geographic structure within either group, but they did detect genetic distinctions in indi- viduals from the southernmost pop- ulations in Mexico that would require study of larger samples to establish taxonomic status. Beyond morphology and genetics, another approach to the taxonomic question could focus on whether call notes differ between the eastern and western Curve-billed Thrasher groups. All other North American thrasher species—including Long- billed vs. Brown, and California vs. Crissal vs. Le Conte’s—have species- specific call notes. If the two Curve- billed Thrasher groups are “good” species, they might be expected to have different call notes (J.L. Dunn, personal communication). All of the authors have left open the question of whether the eastern and western groups are sufficiently isolated from each other reproduc- tively to be classified as different bio- logical species (the concept used for ADVERTISEMENT the American Ornithologists’ Union Check-list and, by default, the ABA list). Nevertheless, as Kevin E. Omland remarked in 2001 in his article “Thrashing out species limits in the Southwest: A Curve-billed examination” (Birding 33:320–328), listers would be wise not to end their Curve-billed quest after seeing birds from only one of the two groups. A bird from the other group could be a new ABA-listable species someday.
26 BIRDING • FEBRUARY 2004