Birds of Palmyra Atoll
Palmyra Atoll NWR is the only seabird nesting area available within 450,000 square miles of ocean and an important marine feeding ground. Palmyra Atoll and Johnston Atoll are the only sparsely/uninhabited breeding grounds south of Hawai‘i and north of Jarvis in the Line Islands. Seabird populations residing at Palmyra Atoll are primarily pelagic feeders that obtain the fish and squid they consume by associating with schools of large predatory fish such as tuna and billfish. Breeding seabird pairs and their recently fledged young rely on abundant and local food sources within easy commuting range of the breeding colonies of Palmyra.
Palmyra supports the second largest colony of nesting red-footed boobies (Sula sula) in the world with total population estimates around 6,250 pairs. Due to the high number of nests and varied stages of nesting activity, nesting of the red-footed boobies occurs almost year round on Palmyra. Red-footed boobies' most common nest and roost site is currently Tournefortia argentea along the water’s edge. Surveys conducted in 1992, prior to the recent Pisonia forest decline, showed important colonies of red-footed boobies in Pisonia forests on Eastern, Holei, Bird, and Papala Islands.
The masked booby (Sula dactylatra) has been reported from Whippoorwill, Portsmouth, Holei, Tanager, and the Fighter Causeway at Palmyra Atoll NWR. U.S. Fish and Wildlife Service biologists estimated the Palmyra population of masked boobies at 35 pairs in 2002.
Brown boobies (Sula leucogaster) are seen on the Fighter Causeway at Palmyra Atoll NWR. These birds nest and roost on the ground and regularly forage in the lagoon at Palmyra. Typical pairs of brown boobies lay 2 eggs but only 1 chick survives.
The brown noddy (Anous stolidus) is more common in the interior than along the shoreline at Palmyra. Typically brown noodies nest on open slopes or under vegetation on the ground, but nests at Palmyra have been found in Pisonia, Tournefortia, and coconut trees on Eastern and Sand Island. It is the only species on Palmyra known to use coconut trees for nesting.
Palmyra shelters approximately 20,000 black noddies (Anous minutus), the largest nesting colony in the central Pacific. This species tends to be less pelagic at Palmyra, feeding in flocks over the lagoons and largely concentrated in large colonies. The colonies appear to be shifting locations according to changes in forest composition.
The sooty tern (Onychoprion fuscata), commonly found throughout the tropical Pacific Ocean, is an abundant resident of Palmyra Atoll. Evidence suggests that sooty terns may have two breeding seasons on Palmyra. An estimated 260,000 birds and 126,000 nests were reported in 1987. A 1993 survey estimated a total of 750,000 sooty tern nests at Palmyra. The most recent seabird survey in 2002 found 139,734 sooty terns. The high density of introduced nest-predating rats greatly reduces ground nest success and fledging rates of sooty terns at Palmyra.
The great frigatebird (Fregata minor), which is commonly seen soaring above the atoll, is widespread in the tropical Pacific, Indian, and Atlantic Oceans. This species is notorious for being highly klepto-parasitic, diving in pursuit of other seabirds to force forfeit of catch.
Palmyra Atoll NWR functions as an essential migratory habitat for maintaining global shorebird populations. The rocky shoreline and extensive sand flats that are exposed at Palmyra during low tide are important foraging areas for several wintering migratory shorebirds. Four primary shorebird species winter full-time at Palmyra, however, other species have been known to occur in small numbers.
The Pacific golden plovers (Pluvialis fulva) prefer to forage in open spaces such as low vegetation fields, roadsides, sandy beaches, or mudflats. Direct counts in 1987 and 1992 estimated total population at 75 and 144 plovers, respectively.
Wandering tattlers (Heteorscelus incanus) have been seen in abundance along the shoreline often associated with blocks of coral or concrete remains of bunkers at Palmyra. A survey in December 2001 reported 44 individuals at the atoll.
The tidal flats, beaches, runway, and forested areas of the atoll are an important wintering ground for bristle-thighed curlews (Numenius tahitiensis). The worldwide population estimate of bristle-thighed curlews is only 6,000 individuals. While migrating between Alaska and the South Pacific, more than 200 bristle-thighed curlews spend their winters on Palmyra.
The recorded winter distribution of ruddy turnstones (Arenaria interpres) is not as large as the other shorebirds at Palmyra. Seventy-seven individuals were counted in the 1992 and a 2002 survey observed 39 turnstones.