Bird Observations from R/V Gyre, 31 May 21 June 2003, SWSS Leg 1, Gulf of Mexico

Bird observations from R/V Gyre, 31 May – 21 June 2003, SWSS leg 1, Gulf of Mexico

Mark Tasker and Simon Mustoe

Introduction

Birds were observed incidentally as part of a cruise designed to investigate sperm whale biology in the northern Gulf of Mexico (Figure 1). Bird observations were not part of the objectives of the cruise, so all observations were incidental to other activities. While effort was systrematic, sampling was not.

Methods

Between 31 May and 21 June, observers were located on the flying bridge in open air at 8m above sea level. Their primary purpose was to search for sperm whales and guide interactions with sperm whales by researchers in inflatable boats. Searches were conducted by naked eye, hand-held binoculars and large 25x stand-mounted binoculars. Any birds observed were logged on a customised program recording time date and location (latitude and longitude) of each record. Observations occurred throughout daylight except in moderate or heavy rain. In total 251 hours of observation were undertaken over 1027 nautical miles (1903 km). A total of six observers (a minimum of three at any one time) were used, of whom two are experienced ornithologists. A few additional records were noted by other members of the ship’s scientific staff.

Results

A species list in systematic order is presented below. The locations of sightings are shown in accompanying maps. Cory’s shearwater Calonectris diomedea One seen on 15 June at 29o08’N 87o14’W.

Audubon's shearwater Puffinus lherminiera Nine records (14 individuals) of this species, and an additional ten records (14 individuals) of small, non-specifically identified shearwaters probably of this species (but Manx shearwater could be present).

Wilson's storm-petrel Oceanites oceanicus Band-rumped storm-petrel Oceanodroma castro Both Wilson’s (12 records, 50 individuals) and band-rumped petrels (21 records, 189 individuals) were identified, but the vast majority of records (157 records of 208 individuals) of storm petrels were not specifically identified. Records came from throughout the area, but very few in shallow water and some distinct areas of concentration (Figure 1). Two flocks of birds on the water (37 and 120 birds), not apparently feeding, were seen on the evenings of 17 and 18 June at 28o44’N 88o51’W and 28o43’N 88o56’W respectively. On the 19 June a concentration of petrels were encountered containing both species feeding together. On several occasions, petrels were seen in association with cetaceans including sperm whales.

Leach's storm-petrel Oceanodroma leucorhoa Four individuals seen, one on 3 June 27o07’N 93o4’W, one on 4 June at 27o21’N 94o01’W, one of 5 June at 27o26’N 93o00’W and one on 6 June at 27o18’N 92o52’W.

Brown pelican Pelecanus occidentalis Two flew past ship at 28o43’N 88o39’W on 11 June.

Magnificent frigatebird Fregata magnificens Thirteen individuals and ten records. One landed on the mast of the Gyre on 2-3 June. It was seen roosting during overnight trawl operations and was present also at dawn the next day. Three frigatebirds at approximately 28o30’N 89 o 00’W on 16-18 June were seen circling over sperm whales.

Tropicbird sp. Phaeton sp. Two tropicbirds seen on 31 May. These birds appeared to have red bills and, on this basis, were considered to possibly be red-billed tropicbird P. aethereus; although white-tailed tropicbird P. lepturus could not be ruled out completely.

Masked booby Sula dactylatra Eleven individuals seen, all over deep water and throughout the area surveyed. Some sightings may have been of northern gannet and three unidentified boobies were also seen.

Tricolored heron Egretta tricolor Three seen flying north on 20 June.

Cattle egret Bubulcus ibis Regular sightings of northbound flocks of egrets between 1 and 7 June were all considered likely to be this species (those identified were of this species) (Figure 3). Thirty-two flocks included 290 individuals. Two landed on ship on 7 June (Figure XX). Yellow-crowned night-heron Nyctanassa violacea Two first-year birds seen flying south on 20 June at 27o39’N 90o46’W.

Osprey Pandion haliaetus One flying north on 4 June at 27o25’N 93o48’W.

Pomarine jaeger Stercorarius pomarinus Three birds seen, two on 6 June at 27o13’N 92o21’W and 27o19’N 92o54’W and one on 17 June at 28 o37’N 88o53’W. One unidentified jaeger was also seen.

Franklin’s gull Larus pipixcan One on 07 June at 27o43’N 91o18’W.

Laughing gull Larus atricilla The most frequently sighted gull: 31 individuals in 26 sightings. Majority of sightings were of first year birds, with only one full adult seen. Ring-billed gull Larus delawarensis One seen on 2 June at 27o29’N 93o58’W and another on 13 June at 28o49’N 87o10’W.

Lesser black-backed gull Larus fuscus One seen on 13 June at 28o58’N 87o50’W.

Royal tern Sterna maxima A total of fourteen individuals seen, all as singles except for a flock of five at 29o10’N 87o30’W on 13 June.

Sandwich tern Sterna sandvicensis A total of fifteen individuals seen in ten sightings.

Common tern Sterna hirundo Six individuals seen in three sightings on 3 and 12 June.

Forster's tern Sterna forsteri One seen on 31 May.

Roseate tern Sterna dougalli One sighting at 27o24’N 92o59’W on 5 June.

Black tern Chilidonias niger A total of 174 individuals seen in 9 sightings on 12-15 June in eastern part of survey area (Figure). Two large groups (47, 90) were associated with large Sargassum mats on 13 June. These concentrations were in ‘green’ water, the result of outflow from the Mississippi accumulating in a warm core eddy. Bridled tern Sterna anaethetus Twenty-two sightings including 75 individuals scattered throughout the survey area. Several larger (10+ individuals) groups seen on 14 June. A further 59 unidentified terns were probably this species. A number of mixed flocks of bridled tern and brown noddy were observed. On at least one occasion, these were in association with small cetaceans.

Sooty tern Sterna fuscata One sighting on 1 June at 26o58’N 94o41’W and one on 16 June at 28o51’N 88o23’W.

Brown noddy Anous stolidus Sixteen birds seen in six sightings between 11 and 19 June in eastern part of area surveyed.

Common nighthawk Chordeiles minor One flew past ship on 7 June at 27o42’N 91o16’W.

Barn swallow Hirundo rustica One seen briefly on 9 June at 27o31’N 90o43’W.

Yellow warbler Dendroica petechia One bird (Caribbean ‘Golden’ race) on and around ship on 8 June at 27o29’N 90o40’W.

Cape May warbler Dendroica tigrina One on board ship on 7 June at 27o34’N 91o06’W.

Discussion To be prepared after literature review.