Socorro Dove

The Socorro dove is a medium-sized, principally terrestrial dove with long legs for a zenaida dove. It is 26.5–34 cm (10.4–13.4 in) long and weighs 190 g (6.7 oz) on average. In overall color pattern, it agrees with its relatives. It is considered to be a stronger-colored insular representative of the mourning dove. The male is deep cinnamon on its head and underparts, with an ear streak like its relatives. The nape is blue-grey and the neck has an iridescent pink patch, most prominent after moult. The upperparts are rufous brown. Female and juvenile coloration is slightly duller. The most conspicuous differences from the mourning dove, darker coloration and more well-developed feet, were useful amid the dark lava rock and the shady forests of its island home, where native mammalian predators were absent but constant threats from red-tailed hawks and great frigatebirds were present. The advertising call begins with a disyllabic coo, followed by three single calls, and ends with another disyllabic coo: "Coo-oo, OO, OO, OO, Coo-oo". Each of these five elements takes a little less than one second. The arid and fairly barren Clarión Island, some 400 km (250 mi) west of Socorro, has an endemic subspecies of the mourning dove, Zenaida macroura clarionensis. These birds are roughly intermediate in appearance between the Socorro dove and the mainland mourning doves. …

There is marked behavioral difference to the mourning dove. When Andrew Jackson Grayson discussed the species, he called it the "solitary dove" because he never saw more than one male and one female together. The doves, particularly the adult males, chase away their young as soon as these can fend for their own and the partners split for the time being. This too is believed to be in adaptation to the former dominance of aerial predators, lest local concentrations of birds, let alone young, inexperienced ones, would present easy targets for the hawks. Typical of many birds on islands lacking mammals, Socorro doves also show little fear of humans or introduced predators, including cats, which proved a major factor in its extirpation. The last habitat in which this dove was found is the low seasonally humid forest above 500 m (1,600 ft) ASL. Before the introduction of cats, it seasonally descended into the lowlands where it was "common" in March 1953 for example. It may be that this coincided with the peak of the breeding season, when many birds had dependent young and dispersed widely to gather more varied food. …