Floyd E. Hayes

Taxonomic status of Paraguay’s only endemic bird, the Chaco Nothura Nothura chacoensis (Aves: Tinamidae)

The Chaco Nothura Nothura chacoensis Conover is endemic to the Chaco of western Paraguay. Originally described as a subspecies of the Spotted Nothura N. maculosa (Temminck), it has been regarded by many authorities as a distinct species based on alleged sympatry with N. maculosa. However, an earlier study revealed no differences in cytochrome b sequences between the two taxa. We reanalyzed the geographic distribution and morphological variation of N. chacoensis and N. maculosa in western Paraguay based on museum specimens. There is no locality where specimens of both taxa were collected, thus there is no evidence for sympatry. Morphologically the two taxa did not differ in any size or shape variable. Plumage characters overlapped in a few specimens. We recorded vocalizations from at least four individuals of N. chacoensis within its known range. Its typical territorial song was a very rapid, relatively monotone trill that was virtually identical with the most frequent territorial song of N. maculosa in length, number of notes, rate of notes, and emphasized frequency, and differed substantially from the songs of other species of Nothura. Based on distributional, morphological, biochemical, and especially vocalization data, we conclude that N. chacoensis should be regarded as a subspecies of N. maculosa.

Floating bird nests provide resources for wildlife: ecological roles of vertebrates using Aechmophorus grebe nests at Clear Lake, California

Floating bird nests occur ephemerally in many wetlands, providing resources for wildlife, but the species using such nests and their ecological roles are poorly studied. Grebes (Podicipedidae) construct floating nests anchored to vegetation. During 2010–2017 we studied the vertebrates using nests of the colonially-nesting western grebe (Aechmophorus occidentalis) and Clark’s grebe (A. clarkii) at Clear Lake, California. In addition to both grebe species using each other’s nests for copulation and egg dumping, we identified 47 other species of vertebrates using Aechmophorus grebe nests, including one fish, one amphibian, two turtles, one snake, 39 birds, and three mammals. Ecological roles of vertebrates using grebe nests included: egg dumping (one bird); predation on grebe eggs, chicks, or adults (four birds and three mammals); scavenging on broken grebe eggs (five birds); resting (one amphibian, three reptiles, and 15 birds); foraging for non-avian prey on nests (13 birds) or in adjacent water (five birds); and incidental destruction of grebe eggs (one fish and two reptiles) and nests (many species). Floating grebe nests undergo a process of ecological succession. Egg dumping, predation, and scavenging occur during early stages of nest development and maintenance. Once abandoned, older nests are used for resting or foraging for prey in nearby water. Decomposing nests are colonized by arthropods which are preyed upon by birds. Because floating bird nests increase food web complexity by attracting aquatic, semiaquatic, and terrestrial organisms at all trophic levels, protecting the engineers and their nests should be considered a conservation priority by wetland managers.

Least Grebes (Tachybaptus dominicus) Nesting on a Non-Floating Concrete Structure at Roatán, Honduras

Abstract. Grebes typically build floating nests that are attached to vegetation and very rarely construct nests on non-floating structures. On 29 August 2017, a pair of Least Grebes (Tachybaptus dominicus) was photographed nesting on top of a non-floating concrete structure on a sewage pond at Roatán, Honduras. This observation demonstrates that Least Grebes may nest on artificial ponds lacking sufficient vegetation for constructing and anchoring a floating nest provided that a suitable flat and hard surface is available just above the waters surface.