Parasitic Jaegers: Midair Pirates of September Skies

# What happens when a tern catches a fish

A tern or small gull plunges, resurfaces with a fish in its bill, and begins to fly away. Before it can eat, a dark, swift bird with a sharply pointed tail may appear out of nowhere. It chases the smaller bird, forces a wing nip with its hooked bill, and the fish falls. The jaeger catches that dropped meal in mid-air and swallows it.

# Who the jaeger is

The bird doing the chasing is the Parasitic Jaeger (Stercorarius parasiticus). Jaeger is the German word for hunter. On tundra nesting grounds the species takes the "hunter" part literally, preying on small birds and rodents. For much of the rest of the year it lives on marine waters and uses a different tactic: piracy.

# How jaegers steal food

They don't usually kill larger seabirds. Instead they rely on speed and intimidation. Over flocks of foraging terns and small gulls in late summer and fall, Parasitic Jaegers sprint, twist, and press until a target bird drops its catch. The jaeger then snatches the fish in flight.

This behavior is dramatic but efficient: jaegers expend energy chasing others rather than making their own small dives for fish. The behavior is most visible where terns and small gulls concentrate on productive feeding areas.

# Where and when to watch

Timing: late summer into September is prime for observing jaeger piracy because many terns and small gulls are actively feeding in coastal and some inland waters.

Places mentioned where jaegers turn up inland include Puget Sound, the Great Lakes, and Chesapeake Bay. Anywhere large flocks of terns or small gulls are feeding, jaegers may patrol above.

# What jaegers look and sound like

Parasitic Jaegers are dark, falcon-like birds with sharply pointed tails. Their flight is fast and agile. Their calls and other field recordings are archived at institutions like the Macaulay Library at the Cornell Lab of Ornithology, which provided the Common Tern and jaeger recordings used in the original account.

# Field tips for seeing jaegers

• Watch flocks of terns and small gulls over productive estuaries, bays, and inland feeding areas during late summer and early fall.
• Look for a larger, darker bird that arrives suddenly and pursues individual birds aggressively.

# Credits and sources