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Common Tern
- Migrate as far as Brazil, Ecuador, and Bolivia for winter months
- Breed in colonies consisting of hundreds to thousands of birds
- The Oneida Lake colony is the largest inland colony in New York State
The common tern is the most widespread and abundant tern species in New York, and is the smallest colonial water bird on Oneida Lake. It is characterized by a light grey back, white underbelly, deeply-forked white tail, and a glossy black cap and nape. Immature individuals and winter adults have a bill that is uniformly dark, and they lose enough of their black crown feathers that they appear to be balding. In breeding plumage, the bill is blood red with a black tip. The average common tern is 33-40cm (13-16 inches) in length, has a wingspan of about 71cm (31 inches) and weighs about 120g (4.2oz). One banded individual was found to be 25 years old upon recapture. The common tern’s call is a harsh, rolling "kee-urr," with a downward inflection.
On Oneida Lake, common terns primarily feed on shiners and other small fish up to 4 inches in length, but they will occasionally eat aquatic insects. Terns catch their prey by striking the water during shallow dives or by skimming the water’s surface as they fly over. They have even been seen diving for prey from heights of 20 to 30 feet!
Common terns migrate thousands of miles each winter to as far away as Brazil, Ecuador, and Bolivia, but return between late April and mid-May to historic breeding colonies on Oneida Lake. They inhabit beaches, grassy uplands and rocky shores, but are most often seen around low-lying rock islands. Because they are considered “threatened” in New York State, these islands are protected to prevent disturbance. Colonies may contain several hundred to several thousand birds, and nests are built above the high tide line in sand, gravel, shells or seaweed piles. Nests are scraped together, and then are usually lined with vegetation. A clutch of 2-3 eggs is laid between May and July, and both sexes share incubation duties for 21-27 days. Usually just 1 or 2 of the eggs will survive. One brood per season is typical, but re-nesting is common if the first is destroyed.
In the early 1900's, common terns were almost extirpated in New York State by plume hunters. Protective legislation in 1918 allowed them to make a comeback in the 1920's and 1930's. Today, competition with ring-billed gulls for nest sites, human disturbances, flooding, and predation are the major reasons for low populations. Since 1979, researchers from Cornell University and the NYSDEC have recorded census data for breeding areas, and nesting success has increased as a result of the construction of gull exclosures on some tern nesting islands. Oneida Lake today sees a stable population of approximately 400 tern pairs, which primarily nest on Little Island.
To learn more about the Common Tern ...
