Caspian Tern (Sterna caspia) Nancy Seefelt Status: State Threatened
Pointe Mouillee State Game Area., Monroe Co., MI 8/9/2008 © Jerry Jourdan
(Click to view a comparison of Atlas I to II)
Acrobatic plunge dives and a raucous squawk term, perhaps due to water level fluctuations (Ludwig 1968), habitat features or prey are the calling cards of the Caspian Tern, the availability. Disturbance, contaminant levels largest of the crested terns. This cosmopolitan and fluctuations in fish populations may also species occurs on all continents, except influence Caspian Tern colony locations (Scharf Antarctica. In North America it breeds along and Shugart 1998). the Pacific, Atlantic and Gulf coasts, as well as the Great Lakes, the Prairie Provinces and the During the MBBA I period, 85% of Michigan’s interior west (Cuthbert and Wires 1999). Great nesting Caspian Terns chose Lake Michigan Lakes populations of Caspian Terns are habitats. Only eight blocks were confirmed migratory, and they overwinter in the Gulf and breeding sites, including five Lake Michigan Atlantic states, as well as the Caribbean and as islands, two islands in Saginaw Bay and one far south as northern South America (Cuthbert island in Thunder Bay near Alpena. During the and Wires 1999). MBBA II period, there were still relatively few
confirmed breeding locations (10 blocks in 9 Distribution Township); the distribution of these confirmed The Caspian Tern is not a common breeder in sites included areas in the northern LP (Bay, Michigan, but records indicate that it has a long Alcona, Arenac, Leelanau and Charlevoix history in the state. In 1848, breeding Caspian counties) and in the UP (Delta and Mackinac Terns were documented on small islands at the counties). Caspian Tern sightings have also end of the Garden Peninsula (Delta County) and increased in all areas, but given the relatively also in the Beaver Archipelago of northern Lake low population estimates for the Great Lakes, Michigan (Charlevoix County) by the early many of these observations may be migrating 1900s (Barrows 1912). Many records are birds, foraging individuals (adults may travel available from islands and coasts throughout some distance to find food) and/or other non- Michigan, but traditional nesting locations in breeders (typically this species does not breed northern Lake Michigan appear to be used most until age three) (Cuthbert and Wires 1999). consistently over time. Other areas, including Lake Michigan islands and coastal areas still sites in northern Lake Huron and Saginaw Bay, have been used less consistently over the long-
© 2010 Kalamazoo Nature Center Caspian Tern (Sterna caspia) Nancy Seefelt Status: State Threatened appear to be important nesting locations for that this species is declining in Michigan Caspian Terns in Michigan. (particularly in Lake Michigan), although more terns are nesting elsewhere, including Lake Breeding Biology Ontario (Cuthbert and Wires 2008). Caspian Terns are ground nesters and typically make a simple scrape nest in sand and/or gravel, Conservation Needs usually in areas with sparse vegetation (Cuthbert Although the continental population appears and Wires 1999). The nests are sometimes lined robust, the relatively small numbers of Caspian with dried plants, pebbles, shells and other Terns in the Great Lakes and the decline of this debris (Bent 1921). Caspian Terns typically species at historical nesting locations in Lake return to Michigan in late April or early May. Michigan, led to listing this species as State Eggs are laid as early as May and renesting Threatened in Michigan. There is concern by occurs as late as the latter half of June. When agencies, university scientists, and others that young fledge, they typically stay with their Caspian Terns may continue to decline in the parents in family groups (Ludwig 1968). upper Great Lakes. As many Caspian Terns co- Caspian Tern fledglings enjoy the longest period nest with other species (typically gulls and of parental care of any tern, lasting several cormorants), management actions aimed at these months (Cuthbert and Wires 1999). Birds begin other species (particularly cormorants) have the migration southward in August, with most birds potential to negatively impact Caspian Tern gone by the end of September. reproductive success. In addition, disturbance at the breeding colonies, especially early in the Abundance and Population Trends breeding season, can lead to site abandonment In 2002, the continent-wide estimate for (Cuthbert and Wires 1999). Conservation of breeding Caspian Terns was between 66,000 - breeding habitats, many of which are state and 70,000 birds (Kushlan et al. 2002). The federally owned, is key to protection of this distribution and abundance of colonial species in Michigan. waterbirds in the Great Lakes has been more specifically documented by decadal surveys in 1976-77 (Scharf 1978), 1989-91 (Scharf and Shugart 1998), and 1997-1999 (Cuthbert et al. 2003). Currently, the fourth decadal waterbird census is near completion (Cuthbert and Wires 2008). Breeding pairs of Caspian Terns increased by 86% in the upper Great Lakes between 1977 and 1989; this is possibly due to more tern nesting areas documented in Lake Michigan, but also in other areas including northern Lake Huron (Scharf and Shugart 1998). The number of breeding pairs continued to increase through 1997 (Cuthbert et al. 2003). Over these first three decadal census periods (1976-1977, 1989-1991 and 1997-1999), Caspian Terns have increased in nest numbers (+69.5%) and in the number of active colony sites (+50%) in the Great Lakes (Morris et al. in press). However, the current census suggests
© 2010 Kalamazoo Nature Center Caspian Tern (Sterna caspia) Nancy Seefelt Status: State Threatened Literature Cited American Great Lakes, 1976 – 1999. Journal of Great Lakes Research. Barrows, W.B. 1912. Michigan Bird Life. Scharf, W.C. 1978. Colonial birds nesting on Michigan Agricultural College Special man-made and natural sites in the U.S. Bulletin. Great Lakes. Technical Report D-78-10, Bent, A.C. 1921. Life Histories of North U.S. Army Engineer Waterways Experiment American Gulls and Terns. U.S. National Station, Vicksburg, Mississippi. Museum Bulletin, 113. Scharf, W.C. and G.W. Shugart. 1998. Cuthbert, F.J., J. McKearnan, L.R. Wires, and Distribution and abundance of gull, tern, A. Joshi. 2003. Distribution and abundance and cormorant nesting colonies of the Great of colonial waterbirds in the US Great Lakes, 1989 and 1990. Publication No. 1, Lakes: 1997-1999. Draft report to US Fish Gale Gleason Environmental Institute, Lake and Wildlife Service, Ft. Snelling, MN. Superior State University, Sault Ste. Marie, Cuthbert, F.J. and L.R. Wires. 1999. Caspian Michigan. Tern (Sterna caspia). In. The Birds of North America, No 403. (A Poole and F Gill, eds.). Suggested Citation The Birds of North America, Inc., Philadelphia, PA. Seefelt, N. 2010. Caspian Tern (Sterna caspia). Cuthbert, F.J. and L.R. Wires. 2008. Long- In Chartier, A.T., J.J. Baldy, and J.M. term monitoring of colonial waterbird Brenneman (eds.). 2010. The Second populations in the U.S. Great Lakes: Michigan Breeding Bird Atlas. Kalamazoo improving the scientific basis for Nature Center. Kalamazoo, MI. Accessed conservation and management year 1 and 2 online at:
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