Blue-gray Gnatcatcher, Polioptila caerulea

Blue-gray Gnatcatcher, Polioptila caerulea gracilis. Photograph taken within a residential community in Alamos, Sonora, March 2019. Photograph and identification courtesy of David F Smith, Alamos, Sonora.

Background and Identification

The Blue-gray Gnatcatcher, Polioptila caerulea gracilis, is one of eight subspecies of Blue-gray Gnatcatcher, all eight of which are found in Mexico. They are a member of the Polioptilidae Family of Gnatcatchers, which has twenty-one members placed in three genera, and one of seventeen species of the Polioptila Genus. This species pairs monogamously, and the male contributes significantly to nest construction, incubation, and the feeding of nestlings and fledglings.  Their nests are subject to failure due to Cowbird parasitism and are often preyed upon by a wide variety of birds as well as raccoons, squirrels, and snakes. Blue-gray Gnatcatchers are known in Mexico as Perlite Azul Gris.

The Blue-gray Gnatcatcher is very small in stature, with total lengths ranging from 10 cm (3.9 inches) to 11.5 cm (4.5 inches) and average masses of 5 g (0.18 oz) to 7 g (0.25 inches). The sexes are similar in appearance from September through December; the males have a black forehead and supercilium from January to August. They are an overall bluish-gray color with white underparts, a prominent white eye-ring, and an exceedingly long black tail that has white margins. Their bill has a blackish lower mandible and grayish horn, their iris is brown, and their legs and feet are blackish to neutral gray.

Habitat and Geographical Range

The Blue-gray Gnatcatcher is typically found in moist areas within wooded habitats, and they nest in open scrubby areas. They avoid areas dominated by needle-leaved conifers and usually forage in densely vegetated areas. They glean a wide variety of insects and spiders off foliage and by hovering and sallying forth after they flush prey. They are known for their unique song. They have life spans of up to four years.

The Blue-gray Gnatcatcher is a partial migratory species, with many populations wintering throughout Mexico. A limited number of birds are year-round residents of Mexico. They are found in Baja California, in the interior of Sonora and Coahuila south to southern Chiapas, and on the Atlantic slope from Tamaulipas south to Belize including the Yucatán Peninsula. They are found at elevations from sea level to 2,500 m (8,200 feet). The gracilis subspecies is found only within the foothills of Sonora.

Common Misidentifications

The Blue-gray Gnatcatcher can be confused with the California Gnatcatcher, Polioptila californica, which lacks white outer tail feathers. The Black-capped Gnatcatcher, Polioptila nigriceps, is also a very similar species that has shorter outer tail feathers and a bold dark cap present in mature males. Lastly, the Black-tailed Gnatcatcher, Polioptila melanura, is similar but also lacks the outer white tail feathers.

Conservation Status

From a conservation perspective the Blue-gray Gnatcatcher is currently considered to be of Least Concern with stable, widely distributed populations.