Endangered Species Day: Southwestern Willow Flycatcher & Relict Leopard Frog

2017-05-19 ESD 2 Flycatcher and Frog

Southwestern Willow Flycatcher

Official Status:

Listed Endangered in 1995

Life History:

This subspecies has a grayish-green back and wings, whitish throat, light gray-olive breast, and pale yellowish belly. Two wingbars are visible; the eye ring is faint or absent. The upper mandible is dark and the lower is light. The most distinguishing characteristic between the southwestern willow and other willow flycatchers is their song, a sneezy “fitz-bew”.

The southwestern willow flycatcher is present in breeding territories by mid-May. It builds nests and lays eggs in late May and early June (average clutch size is 2 to 5 eggs) and fledges young in early to mid-July. Second clutches only occur if the first clutch failed. Between August and September, the southwestern willow flycatcher migrates to wintering grounds in Mexico, Central America, and possibly northern South America.

The southwestern willow flycatcher is an insectivore and forages within and above dense riparian vegetation. It catches insects while flying, hovers to glean them from foliage, and occasionally captures insects on the ground.

Distribution and Habitat:

The breeding range of the southwestern willow flycatcher includes southern California, Arizona, New Mexico, extreme southern portions of Nevada and Utah, far western Texas, perhaps southwestern Colorado, and extreme northwestern Mexico. In Nevada this subspecies can be found along the Virgin River, lower Muddy River, Colorado River, and Pahranagat Valley.

The southwestern willow flycatcher breeds in relatively dense riparian tree and shrub communities associated with rivers, swamps, and other wetlands including lakes and reservoirs. In most instances, the dense vegetation occurs within the first 10 to 13 feet above ground. Habitat patches must be at least 0.25 ac in size and at least 30 feet wide. Historically the southwestern willow flycatcher nested in native vegetation including willows, seepwillow, boxelder, buttonbush, and cottonwood. Following modern changes to riparian communities, this subspecies still nests in native vegetation, but also uses thickets dominated by non-native tamarisk and Russian olive, or in mixed native non-native stands. The flycatcher builds a small open cup nest, most often 6.5 to 23feet above ground in a fork or on a horizontal branch of a medium-sized bush or small tree with dense vegetation above and around the nest.

Threats:

This species has declined because of removing, thinning, or destroying riparian vegetation; water diversions and groundwater pumping which alter riparian vegetation; overstocking or other mismanagement of livestock; and recreational development. In addition to above threats, the southwestern willow flycatcher is also subject to cowbird parasitism.

Fun Fact:

Empidonax flycatchers are almost impossible to tell apart in the field so biologists use their songs to distinguish between them.

Source: www.fws.gov/nevada/protected_species/birds/species/swwf.html

Relict Leopard Frog

Official Status:

Candidate

Life History:

The relict leopard frog, Rana onca, has not been found in Utah since 1950. In fact, the species was believed to be completely extinct until three populations were found in Nevada during the early 1990s. The relict leopard frog formerly occurred in Utah along the Virgin River near St. George in Washington County. Biologists are not sure why this species became extirpated from Utah, but dewatering of the Virgin River, hybridization and competition with introduced frog species, and predation by non-native bullfrogs and fishes are all possible explanations.

Because so few relict leopard frogs have been found, little is known about their feeding and reproductive habits. Adults probably eat insects, whereas tadpoles likely eat plants, detritus, and algae. The species may breed in the spring, but exact times are unknown.

Distribution and Habitat:

Adult frogs inhabit permanent streams, springs, and spring-fed wetlands below approximately 600 m (1,968 ft). Adults may prefer relatively open shorelines where dense vegetation does not dominate. Breeding habitat includes pools or slow moving side areas of streams, with or without emergent vegetation.

The historical distribution of this species is not well documented. The distribution has historically been characterized as springs, streams, and wetlands within the Virgin River drainage from the vicinity of Hurricane, Utah to the Overton Arm of what is now Lake Mead, Nevada, and along the Muddy River in Nevada. The species may have once been present on the Colorado River mainstem. Populations in Utah appear to have been extinct since the 1950s.

Threats:

Elimination or dramatic alteration of aquatic habitat due to dams, agriculture, marsh draining, and water development and the spread of predator and nonnative bullfrogs, crayfish, and predaceous fishes and a fungal disease, chytridiomycosis.
Source: www.fws.gov/nevada/protected_species/amphibians/species/relict_leopard_frog.html

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One Response to “Endangered Species Day: Southwestern Willow Flycatcher & Relict Leopard Frog

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