Research ArticleECOLOGY

Warm oceanographic anomalies and fishing pressure drive seabird nesting north

See allHide authors and affiliations

Science Advances  26 Jun 2015:
Vol. 1, no. 5, e1400210
DOI: 10.1126/sciadv.1400210
  • Fig. 1 Elegant Tern population data.

    Population growth rates: (A) Growth rate of nesting pairs on Isla Rasa between 1980 and 2014. Before rodent eradication in 1995, mean annual growth rate in the Midriff was 0.046, increasing after to 0.077. The dotted line projects the pre-1995 trend to highlight the difference with the post-1995 real values. (B) The growth rate of nesting pairs after 1991 in all three California colonies taken together was 0.14. In both models, only the data points from normal years (gray symbols) were taken into account to fit the equations. Relationship between Isla Rasa and San Diego Bay: (C and D) Elegant Tern colony size (nesting pairs) in Isla Rasa (C) compared against colony size in San Diego Bay (D). In all plots, yellow points indicate years in which nesting collapsed in the Midriff, and red dots indicate strong El Niño years in the Pacific Ocean.

  • Fig. 2 Time series correlations between oceanographic variables, fisheries, and Elegant Tern nesting populations.

    (A) Proportions of Elegant Tern nests established in California in relation to total nests counted. (B) Midriff winter-spring SST anomaly. (C) SST difference between the Pacific and Midriff. (D) Fishing effort by the Sonora fleet. (E) Total sardine landings. (F) SST anomalies in the Gulf of California and the Pacific. Top images depict the general winter-spring conditions during normal and El Niño cycles: (i) February 2013, a highly productive year with cool surface temperatures; (ii) February 1998, the most intense El Niño of the last decades. Lower images show the formation of a local anomaly during a non–El Niño year: (iii) April 2009, an apparently normal year, transitioned in (iv) May 2009 into a high SST condition in the Gulf of California that forced most of the nesting terns to abandon the area. (G) Elegant Tern carrying a Northern Anchovy to feed its chick (photo by P. Robles-Gil). (H) Network of significant path relationships between variables: Numerical values with black arrows indicate path coefficients; white arrows indicate the lumped influence of unidentified extraneous variables. Variables identified with label “(t − 1)” have a 1-year-lag influence on the decision by nesting terns to migrate away from the Midriff.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/5/e1400210/DC1

    Fig. S1. Demographic spillover from Isla Rasa into San Diego Bay.

    Fig. S2. Local oceanographic anomalies in the Gulf of California.

    Table S1. Elegant Tern demography data.

    Table S2. Fisheries data.

    Table S3. Oceanographic data.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Demographic spillover from Isla Rasa into San Diego Bay.
    • Fig. S2. Local oceanographic anomalies in the Gulf of California.
    • Table S1. Elegant Tern demography data.
    • Table S2. Fisheries data.
    • Table S3. Oceanographic data data.

    Download PDF

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article