| Kirtland's Warbler | |
|---|---|
 | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Parulidae |
| Genus: | Setophaga |
| Species: | Setophaga kirtlandii |
Kirtland's Warbler or Jack Pine Warbler (Setophaga kirtlandii) is a rare species of New World warbler.
Description[]
These little birds have a bluish-gray back and a yellowish belly. Males have broken eye white eye rings. Females have lighter backs and paler stomachs. Fledglings have dark gray stomachs and are a lot smaller. With the adult length at 14-15 cm (5.5-5.9 in), the species is the largest Setophaga warbler.
Behavior[]
Kirtland's Warblers prefer to nest in the lower branches of young jack pine forests. Males are harder to see than females and are normally only visible during breeding months. They are part frugivore and part insectivore.
Occurrence[]
Kirtland's Warblers are restricted to the Lower Peninsula, but occasionally nest in Ohio, Wisconsin, and Canada. The warblers are most common in Grayling areas. Sometimes seen in Hartwick Pines State Forest.
History[]
Kirtland's Warbler's status as a near-threatened species is at least partially due to the fact that they are highly selective about their habitat. They breed exclusively in a restricted area where the southern edge of the large Pinus banksiana forests covers a peculiar, sandy ground. This type of ground is important to these birds because their nests, located in the grass or low in the pine trees, would be submerged by the frequent summer rainstorms were the water not quickly drained by the sand. Plus, they only nest among 8-22 year old pine trees. Another aspect of their lifecycle that makes these warblers vulnerable is their migration to the Bahamas. Kirtland's Warbler was first discovered in 1841, when an individual was found on a ship on its way to the Bahamas. It took over 60 years to find a nest, and around that time, the large-scale burning and cutting down of mature Jack Pine forests and the resulting growth of younger trees in northern Michigan had created the most favorable habitat these birds had ever known. Kirtland's Warblers are among the few birds whose population increased despite human immigration to the West. But they weren't the only species that benefited from the drastic changes in their habitat. The clearing of the old forests attracted Brown-headed Cowbirds to northern Michigan, and the arrival of these brood parasites caused a sharp decline in Kirtland's Warbler population. When the warblers were counted for the first time in 1951, there were about 500 couples and 55% of the nests contained cowbird eggs; the generation of young warblers was reduced by a third. By 1971, there were only 200 warbler couples left, and the cowbirds had occupied four nests out of five. So, a program to eliminate Brown-headed Cowbirds began, and thousands of these birds were caught every year since 1972. Before this program was started, each Kirtland's Warbler couple generated one fledgling per year on average; now, the number has increased to four. Despite this, the number of breeding couples changed rather slowly. There were 200 couples in 1972, and 200 6 years later. By 1985, the population had increased to about 440 breeding couples. This is perhaps due to the high mortality rates of young warblers during their first migration. Ever since 1987, thanks to government intervention to prevent the natural growth of Jack Pine forests, the species' population has been growing more steadily. Between 1987 and 1990, suitably aged habitat doubled, and by 1994, more than 500 singing males were counted. The current population is 4500-5000 and growing.
Gallery[]
