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.

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. They are known in Mexico as perlite azul gris.

The Blue-gray Gnatcatcher is very small in stature. The sexes are similar in appearance however 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.

The Blue-gray Gnatcatcher are typically found in moist areas within wooded habitats and nest in open scrubby areas. They avoid areas dominated by needle-leaved conifers. They forage in denser vegetation. They glean a wide variety of insects and spiders off foliage and by hovering and sallying 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 migrator with the majority of birds being short to long range migrators that winter throughout Mexico. A limited number of birds being year-round residents. They are found in Baja California, and in the interior of Sonora and Coahuila and south to southern Chiapas and on the Atlantic slope from Tamaulipas south to Belize including the Yucatán Peninsula being found from sea level to elevations of 2,500 m (8,200 feet). The gracilis subspecies is found only within the foothills of Sonora.

They are a short to long migrator known to winter throughout Mexico.

They pair monogamously with the male contributing significantly in nest construction, incubation, and the feeding of nestlings and fledglings. Their nests are subject to failure due to Cowbird parasitism. Their nests are also preyed upon by a wide variety of birds as-well-as racoons, squirrels, and snakes. Adults mob potential predators and obtain support from other small birds.

The Blue-gray Gnatcatcher can be confused with the California Gnatcatcher, Polioptila californica (lack white outer tail feathers), the very similar Black-capped Gnatcatcher, Polioptila nigriceps (shorter outer tail feathers; males bold dark cap), and the Black-tailed Gnatcatcher, Polioptila melanura (lack white outer tail feathers).

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