Seabirds of Hawaii

1997

Ibis

146

We studied flight direction relative to wind direction (hereafter referred to as “flight direction”), the relation between wing morphology and flight behaviour and interspecies relationships in flight behaviour among all major seabird taxa. We calculated wing loading and aspect ratios for 98 species from 1029 specimens. Species were sorted into 13 groups on the basis of similarity in patterns of flight direction. The primary flight direction of Pelecaniformes and Charadriiformes was into and across headwinds. The most common flight direction of Procellariiformes was across wind. Seabirds avoided flying with tailwinds. Wing loading and aspect ratios were positively correlated in Procellariiformes, Pelecaniformes and alcids but negatively correlated in larids. In Procellariiformes, incidence of headwind flight and that of tailwind flight were significantly correlated with wing loading and aspect ratio; species with higher wing loading and aspect ratios flew more often into headwinds and less often with tailwinds. In contrast, the proportion of Pelecaniformes and Charadriiformes flying with tailwinds increased significantly with increased wing loading. Our results demonstrate a close link in seabirds between flight behaviour, wing morphology and natural history patterns in terms of distribution, colony location, dispersal and foraging behaviour.

Section: Wing Morphology In Relation To Reproductive Strategies and Dmentioning

confidence: 99%

Flight behaviour of seabirds in relation to wind direction and wing morphology

1997

Ibis

146

“…The data included 681 survey-days during spring, 505 during autumn, 395 in El Niño, 563 in the Neutral phase and 228 in La Niña. 1980, 1987, 1991, 1992, 1993, 19951986, 1987, 1991, 1994Neutral 1984, 1986, 1990, 19941983, 1985, 1989, 1990, 1992, 1993La Niña 1985, 19891984, 1995 We conducted a second mega-scale regression to compare ENSO and current system relationships among the five populations. We grouped survey data for each population into one data set with 'population' as one of the independent variables.…”

Section: Statistical Analysesmentioning

confidence: 99%

“…We included two geographical variables, distance to colony and distance to nearest point on the mainland, because many colonies of aethereus are located on the mainland shoreline. For northern rubricauda populations, all distances to colony are those to the Leeward Hawaiian Islands (Midway Island was used as the focal point), where roughly 90% breed (Harrison 1990); for northern lepturus we used Kauai. The number of birds is not known for many colonies of southern rubricauda, southern lepturus or aethereus; for those we used distance to the nearest known major colony of each population (Fig.…”

Section: Statistical Analysesmentioning

confidence: 99%

“…The at-sea distributions of these species in the ECP have been well described .The feeding and social behaviours of rubricauda and lepturus at sea have previously been described briefly (Gould et al . 1974, Harrison 1990, Schreiber & Schreiber 1993). However, little information is available on the at-sea behaviour of aethereus , nor are we aware of studies describing the responses of these species to the physical environment, either from small-scale (20-60 km;Hunt & Schneider 1987) or larger-scale (> 1000 km) perspectives.…”

mentioning

confidence: 99%

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At‐sea behaviour and habitat use by tropicbirds in the eastern Pacific

2005

Ibis

During the boreal spring and autumn 1980–95, we surveyed Red‐tailed Phaethon rubricauda, White‐tailed P. lepturus and Red‐billed Tropicbirds P. aethereus at sea in the eastern Pacific. Two subpopulations were indicated for both rubricauda and lepturus, based on distribution hiatuses near the South Equatorial Current (see companion paper). Thus, five populations were examined, two each of rubricauda and lepturus, and one of aethereus. During the boreal spring, when equatorial current systems are less well developed, geographical variables (distance from nearest colony and nearest land) were the most important variables affecting tropicbird occurrence. However, sea‐surface salinity and thermal structure of the water column were the primary variables delineating tropicbird occurrence during the boreal autumn. Each tropicbird species utilized different species/sizes of aquatic predators (that make their prey available at the surface) that in turn utilize different oceanographic environments. We suspect that the distribution of aquatic predators is primarily responsible for colony locations and distribution of tropicbird species in the eastern Pacific.

“…1974). Harrison (1990) estimated total abundance (i.e. adults and subadults) for the same area exceeding 75 000 birds, including 50 000 birds (of which a maximum of 24 130 were breeders) from the Hawaiian Islands.…”

mentioning

confidence: 99%

At‐sea distributions and abundance of tropicbirds in the eastern Pacific

2005

Ibis

During spring and autumn 1980–95, we surveyed Red‐tailed Phaethon rubricauda, White‐tailed P. lepturus and Red‐billed Tropicbirds P. aethereus at sea in the Pacific between the coast of the Americas and 176°W. For the Pacific, we had complete coverage of the range of aethereus, but only partial coverage of that of rubricauda and lepturus. Six areas of higher density were indicated: three of rubricauda, two of lepturus and one of aethereus. After pooling data across years, the ‘abundance’ (total number including subadults and adults) estimate for rubricauda was 81 700 (boreal spring) and 86 500 (boreal autumn) birds. Abundance of each of the three rubricauda subpopulations differed between seasons by about 50% despite seasonal consistency when populations were grouped. Furthermore, high densities of rubricauda occurred at the edge of our study area, indicating that neither of the seasonal estimates for this species could be considered as total numbers. Abundance estimates of lepturus during the non‐breeding season (when these birds had dispersed from colonies) were 11 000 and 41 500 birds for northern and southern populations, respectively. Estimated abundance of aethereus during the boreal spring was 26 700 birds, and 33 400 during the boreal autumn. Because tropicbirds are attracted to survey vessels, we also estimated the abundance after excluding those recorded as flying in a steady direction, or having been attracted to the ship. Considering only stationary birds (i.e. those that could not have been attracted), our minimum estimates were 41 000 rubricauda, 15 750 aethereus, 28 000 southern lepturus and 6400 northern lepturus.