White-winged dove

Appearance

White-winged doves are a plump medium sized bird, at 29 cm from tip to tail and a mass of 150 g. They are brownish-gray above and gray below, with a bold white wing patch that appears as a brilliant white crescent in flight and is also visible at rest.

Adults have a patch of blue, featherless skin around each eye and a long, dark mark on the lower face. They have a blue eye ring and their legs and feet are brighter pink/red. Their eyes are bright crimson, except for juveniles who have brown eyes. Juveniles are duller and grayer than adults and lack iridescence. Juvenile plumage is usually found between March and October.

Differentiating between sexes is difficult, and usually requires examination of the cloaca. Males do have a more iridescent purple color to the crown, neck and nape as well as a more distinctive ear spot, though the differences are slight. Males are usually heavier on average, but differences in daily weight due to feeding make this an inaccurate field tool. Thus most observers cannot accurately differentiate between sexes based on external characteristics alone.

The identifying hallmark is its namesake white edged wing, which similar species lack. It appears similar to the mourning dove, with which it may be easily confused. Compared to the mourning dove, it is larger and heavier. It has a short rounded tail, whereas the mourning dove has a long, tapered triangular tail. The mourning dove has several black spots on the wing; the white winged dove does not. Other similar species include the white-tipped dove, but the lack of white wing edging is distinctive. The same goes for the invasive Eurasian collared dove, which is further differentiated by grayish overall color and black neck band.

Their molt is similar to that of the mourning dove. Molting runs June through November, and occurs in the summer breeding grounds unless interrupted by migration.

Distribution

Some populations of white-winged doves are migratory, wintering in Mexico, Central America, and the Caribbean. They are year-round inhabitants in Texas. San Antonio, Texas, had a year-round population of over a million doves in 2001. The white-winged dove inhabits scrub, woodlands, desert, urban, and cultivated areas. They are found increasingly far north, now being visitors to most of the United States, and small parts of southern Canada.

Status

The United States Fish and Wildlife Service has tracked the population of the mourning dove for decades. The United States population peaked in 1968, but fell precipitously in the 1970's. The decline is likely due to loss of large nesting colonies in the 1960’s and 1970’s from habitat destruction, shifts in agricultural trends, and over-hunting. The population has continued to decline despite tougher hunting laws. Its population and range in Arizona has sharply contracted, though its range continues to expand in Texas. Even though it is the second most shot-hunted bird in the United States, it remains poorly studied, especially in California, Florida, as well as in Mexico.

Lead poisoning, especially in hunting areas, poses a significant risk to white-winged dove health. A 2010 Texas study found that 66% of doves had elevated lead levels. The study noted that birds with lethal concentrations of lead were not found because accidental ingestion of lead shot can kill birds in just two days, and that they are incapacitated before that point, meaning that such birds died before they could be collected by researchers.

Climate change is expected to expand their range to the north, but will also threaten populations with increased drought and fire, which destroy habitat, and spring heatwaves which can kill young in the nest.

Colonial nesting sites in Mexico have seen significant losses. The main causes were brush clearing to make way for agricultural or urban development, extreme weather such as droughts and hurricanes, and over-hunting. The population in Mexico followed the trend of American populations. In the 1970's, there were only a million birds in northeastern Mexico, compared to a rebound of 16 million in the 1980's, and five million in 2007. Habitat fragmentation is of great concern to the species, especially due to the preference for returning to the same large colonies year after year. Due to continued pressures, large nesting colonies are now mainly gone, and are not expected to return. Despite this, the white-winged dove has proved adaptable to human disturbance, and is regarded as a species of least concern by the International Union for Conservation of Nature.

Behavior

Flocks of up to a million birds have been recorded.

Reproduction

To impress females, males circle them with tail spread and wings raised. Males and females work together in raising the young. It builds a flimsy stick nest in a tree of any kind and lays two cream-colored to white, unmarked eggs. One chick often hatches earlier and stronger, and so will demand the most food from the parents. A dove may nest as soon as 2–3 months after leaving the nest, making use of summer heat. The dove will nest as long as there is food and enough warmth to keep fledglings warm. In Texas, they nest well into late August. Families and nestmates often stay together for life, perching and foraging together.

They have better nesting success when in mesquite or tamarix trees. Breeding occurs in two peaks in the summer, although the timing of their breeding varies among years. The peak breeding times for these desert doves occur from May-June to July-August. Breeding in urban areas also occurs in two peaks but may be somewhat offset in timing compared to the desert birds. By early September, most of the adult birds have already begun the migration south. The young leave soon after.

Eggs are relatively small compared to bodyweight, as white-winged doves invest more energy in feeding altricial young instead of laying large eggs that would enable precocial young.

They will return to the same nesting site year after year, sometimes rebuilding a nest in the exact location it was the year before.

Males attend to the nest for the majority of the day, except for foraging breaks during the mid-morning and late afternoon while the female watches the nest. At night, females watch the nest, the male roosts nearby.

Juvenile feathers begin to replace the natal down by seven days old. The prejuvenile molt is complete around 30 days old.

Food

White-winged doves are granivorous, feeding on a variety of seeds, grains, and fruits. Western white-winged doves migrate into the Sonoran Desert to breed during the hottest time of the year because they feed on pollen and nectar, and later on the fruits and seeds of the saguaro cactus. They also visit feeders, eating the food dropped on the ground. Unlike mourning doves, they corn and wheat right off the head. This gregarious species can be an agricultural pest, descending on grain crops in large flocks.

White-winged doves have been found to practice collaborative feeding. Observations in Texas revealed that some bird were shaking seeds from a Chinese tallow tree for the benefit of those on the ground. Mourning doves may represent a vector to spread the invasive Chinese tallow tree, by defecating undigested seeds.

Agricultural fields, especially cereal grains, are a major source of forage. However, they provide less nutrition and protein content, which limit productivity. Having access to significant amounts of native seed is important to ensure that nestlings fledge and are healthier. This is made even more critical by the fact that white-winged doves do not supplement their diet with insects while raising young, unlike many other grain eating birds.