Geology topics

Jay Pitocchelli

Publications and source records attributed to Jay Pitocchelli.

3 recordsLinked to original sources

USGS2003

Variation in plumage, molt, and morphology of the Whiskered Auklet ( Aethia pygmaea ) in Alaska

We studied molt and size variation in Whiskered Auklets collected at sea in August from the Aleutian Islands in 1992 and 1993. We evaluated size differences from external and skeletal measurements. Adults were molting extensively in August, indicating that molt began in July. Primaries 1-5 had been completely replaced, while primaries 6-8 were in various stages of replacement, and primaries 9 and 10 were old in most birds. We also found that juveniles were not molting. This pattern is similar to other species of small auklets where breeding and molt in adults overlap, but juveniles do not molt until the following summer. This suggests that Whiskered Auklets are subjected to similar ecological constraints as other auklets. We provide the first skeletal measurements of Whiskered Auklets and some new external measurements. Results of statistical analyses indicate that there is no sexual dimorphism in adults. A small sample of juveniles suggests that they are similar in size to adults.

Journal of Field Ornithology↗

USGS1994

Using stable isotopes to determine seabird trophic relationships

1. The stable isotopes of nitrogen (δ 15 N ) and carbon (δ 13 C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird trophic positions. 2. Based on δ 15 N analyses, seabird trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower trophic-level organisms are more important to several seabirds than was recognized previously. 3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference. 4. In general, stable-isotope analysis to determine trophic level offers many advantages over conventional dietary approaches since trophic inferences are based on time-integrated estimates of assimilated and not just ingested foods, and isotopic abundance represents a continuous variable that is amenable to statistical analysis.

Alaska, British Columbia↗

USGS1994

Morphological and genetic divergence among Alaskan populations of Brachyramphus murrelets

We studied morphological and mitochondrial DNA (mtDNA) divergence among three populations of Brachyramphus Murrelets: Kittlitz's Murrelets ( B. brevirostris ), and tree-nesting and ground-nesting Marbled Murrelets ( B. marmoratus ). We found little morphological divergence in external and skeletal measurements among Marbled Murrelets, but both populations were easily distinguished from Kittlitz's Murrelets. Principal components analysis (PCA) of external measurements showed that Kittlitz's Murrelets occupied a distinct cloud in multivariate space separate from Marbled Murrelets. However, tree-nesting and ground-nesting Marbled Murrelets were indistinguishable. We obtained the same pattern from PCA of skeletal dimensions. Analysis of mtDNA revealed an estimate of sequence divergence of 4.4%-5.0% between Marbled Murrelets and Kittlitz's Murrelets, suggesting a divergence of about 2.2 MYBP. The difference between ground- and tree-nesting murrelets was 0.03%. This analysis suggests little divergence has occurred between tree- and ground-nesting populations of Marbled Murrelets.

Alaska↗