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Marsh Wrens (Cistothorus palustris) destroyed Yellow-headed Blackbird (Xanthocephalus xanthocephalus) eggs presented on wren territories and probably disrupted at least 10 of 189 yellowhead nesting attempts. Male yellowheads discriminated among Marsh Wren, Song Sparrow (Melospiza melodia), and Common Yellowthroat (Geothlypis trichas) songs, with the greatest proportion of aggressive approaches in response to broadcast Marsh Wren songs. The proportion of aggressive approaches by male yellowheads to Marsh Wren playbacks beside yellowhead nests was 27% and did not change with the stage of the nest; but the proportion of aggressive responses by females did vary, and was highest (53%) in response to playbacks beside nests containing eggs. Male responses are interpreted as reflecting territorial defense against Marsh Wrens, and female responses as a localized nest defense against egg predators.

During a study of migrating land birds in 1987, we examined over 9,200 individual birds representing 99 species from the Saint Croix River Valley, a Lyme disease-endemic area of east central Minnesota and northwestern Wisconsin. We found that 250 deer tick (Ixodes dammini) larvae and nymphs infested 58 birds from 15 migrant species; 56 ticks (22.4%) were positive for the Lyme disease spirochete Borrelia burgdorferi. Five ground-foraging migrant bird species favoring mesic habitats, veery (Catharus fuscescens), ovenbird (Seiurus aurocapillus), northern waterthrush (S. novaboracensis), common yellowthroat (Geothlypis trichas), and swamp sparrow (Melospiza georgiana), accounted for nearly three-quarters of parasitized individuals. Nearly half of the spirochete-positive ticks were removed from migrating birds taken in a riparian floodplain forest. Recaptured migrants with infected ticks indicate that they transmit B. burgdorferi to hexapod larvae. We suggest that birds may be both an important local reservoir in the upper Mississippi Valley and long-distance dispersal agents for B. burgdorferi-infected ticks to other regions of the continent.

The Black-polled Yellowthroat (Geothlypis speciosa) is a little-known species whose range is restricted to a small portion of the TransMexican Volcanic Belt from the Valley of M6xico westward to Lago Pitzcuaro, Michoacin and Lago Yuriria, Guanajuato (fig. 1). It was originally described from "M6xico" by Sclater (1858:447) from three specimens (adult and "young" male and female-) from a collection made by Henri L. F. de Saussure. Sumichrast (1869:546), writing on the geographic distribution of "Native birds of the Department of Veracruz," apparently first made the erroneous assignment of the species to the Orizaba region of Veracruz when he wrote: "Geothlypis speciosa. Alpine region. To this species I refer a Geothlypis occurring in the alpine region among the mountains of Orizaba and which belongs to the collection of my friend M. Mateo, Botteri." Salvin and Godman (1879:152) cited only Sclater's types and a female without locality in their collection, and referred to the above statement of Sumichrast. Ridgway (1902:683) first used the misleading common name "Orizaba Yellowthroat." He was followed by Hellmayr (1935:442) and Moore (in Miller et al. 1957:262). The appropriate common name Black-polled Yellowthroat was, I believe, coined by George M. Sutton (1951). Hellmayr (loc. cit.) cited a specimen taken by W. W. Brown at "Mexico (San Mateo)" and added, this locality was "presumably in the mountains of Veracruz," apparently basing this assumption on Sumichrast's statement. Brown's San Mateo was shown to be in the Lerma Valley by Lea and Edwards (1950; see also Dickerman 1965). However, six years later, Moore (in Miller et al., loc. cit.) cited Brown's San Mateo as in the Valley of M6xico and thus prematurely provided the first literature reference to the species from the Valley. Moore! also followed Hellmayr in citing Orizaba as the probable type locality. Actually, the species does not occur east of the Valley of Mexico, some 200 miles west of Orizaba, and all published records from the Valley of M6xico or eastward to date should be disregarded. I believe the only specimens from the Valley of M6xico are those discussed below. In connection with studies on the Song Sparrows (M lospiza melodia) of the Mexican Plateau (Dickerman 1963), and in subsequent studies on other fresh water marsh species, I have made the first collections of Geothlypsis speciosa from the Valley of M6xico. I also collected the first series of the species in fresh plumage from the western portion of its range, as well as additional series from the headwaters area of the Rio Lerma where most of the known specimens of the species were collected. Within these series there are two dis

Studies of the timing and extent of molt in congeneric species of migratory birds have revealed striking interspecific differences that reflect molt adaptation at the specific level (for example, see Johnson, 1963). However, with the exception of Miller's (1928) work on the Loggerhead Shrike (Lanius ludovicianus), little attempt has been made to explain intraspecific variation in the timing and extent of molt in a migratory species in terms of adaptations at the subspecific level. The Orangecrowned Warbler (Vermivora celata) is a suitable species for such a study because it includes four well-marked geographic races which vary greatly in the extent and location of the breeding range, in the distance and period of migration, and in the timing of breeding. V. c. celata occupies a wide longitudinal range from central Alaska and the Alaskan peninsula eastward across Canada to western and central Ontario. V. c. orestera and V. c. lutescens, in contrast, occupy extensive latitudinal ranges. However, lutescens, which is found from southeastern Alaska to southern California, breeds along the Pacific coast and in the coast ranges, while orestera, an inland race, breeds in the Rocky Mountains and mountains of the Great Basin. V. c. sordida is restricted to the Channel Islands off the coast of southwestern California and to limited coastal areas on the adjacent mainland (ranges in all subspecies, A.O.U. Check-list, 1957). Furthermore, with the exception of an investigation of the Yellowthroat (Geothlypis trichas brachidactylus) by Stewart (1952), there has been, to my knowledge, no detailed study of molt in a parulid. Therefore, a study of the extent, sequence, and timing of the molt in the Orange-crowned Warbler was undertaken to determine the type and degree of possible interracial differences and to see if these differences represented adaptations at the subspecific level.

"Se presenta el primer registro de la mascarita pico grueso (Geothlypis poliocephala) para la región del Eje Neovolcánico Transversal, México. Los sitios donde registramos/capturamos esta especie se encuentran en los suburbios de la ciudad de Morelia, 427 marriba del ámbito altitudinal descrito para la especie. Esto puede deberse a 2 factores: 1) la urbanización que genera hábitats propicios para la especie en su periferia, y 2 ) el incremento de la temperatura en la región en la que se encuentra la ciudad de Morelia. Ambos factores facilitan que esta especie de tierras bajas pueda habitar en áreas de mayor altitud. Así, nuestros registros sugieren que la mascarita pico grueso puede catalogarse como especie potencial a utilizar hábitats suburbanos cuando éstos son similares a los hábitats en los que se distribuye de manera natural."

We compared the relative infectivity to vector ticks of gray catbirds (Dumetella carolinensis) and white-footed mice (Peromyscus leucopus) for the Lyme disease spirochete (Borrelia burgdorferi). Of 28 catbirds captured in a site enzootic for this agent, 18 were infested by immature Ixodes dammini, the tick vector. By comparison, each of 32 mice sampled concurrently from the same site was infested, and by about 10 times as many ticks as were found infesting the 3 most commonly netted bird species. Although 76% of noninfected larval ticks placed on these mice in a xenodiagnosis became infected, none of the ticks similarly placed on 12 catbirds did so. Spirochetes were detected in ticks derived from 2 Carolina wrens (Thryothorus ludovicianus) and a common yellowthroat (Geothlypis trichas), but these species' potential contribution to infecting ticks does not compare with that of mice. Thus, although birds may help establish new foci of ticks, catbirds, at least, do not appear to contribute as reservoirs of infection.

A study of the avifaunas of three different types of bog-black sprucetamarack, white cedar-tamarack and open bog-at approximately the same latitude in central Michigan, indicated that only the black spruce-tamarack bog attracted boreal species of birds during the breeding season. The bog characterized by white cedar had species found in deciduous forest and edge habitat. Few, if any, bird species appear to be closely associated with white cedar. Open dry bogs had only species occupying early successional habitats and no boreal species of birds. The common yellowthroat (Geothlypis trichas) and song sparrow (Melospiza melodia), early successional or ecotonal species having small territories, were the only species found in all three types of bog in central Michigan. It appears that at least the structure of the vegetation and plant species composition determine which boreal species of birds inhabit these isolated bogs.

Adaptive radiation is reflected in the correlation of foraging habits and mensurations of the pelvic skeletal appendages of five species of parulid warblers. The Black-throated Green Warbler, a general crown foliage gleaner, is considered the most generalized of the group. The Yellowthroat is adapted to a reed-shrub-tall-grass habitat by means of a long pelvic appendage and long toes necessary for security of perch in this habitat. The Black-and-White Warbler, with shorter distal segments, a long hallux, and a considerable unaual arc, is at an advantage in clambering over the trunks and larger limbs of trees. The short pelvic appendage of the Ovenbird is compensated for by equilibrating tail-lifting and wing-flicking movements as it forages on a leaf-littered forest floor. A longer third digit in the Redstart, the only significant difference from the Black-throated Green, may aid in rapid take-offs in pursuit of flying insects. Adaptive radiation- in warblers as exemplified by variation in the hind limb appears to be quite extensive and reflects the spread of the group into many niches. Sympatry may well have reinforced such