Brown Pelicans, Pelecanus occidentalis californicus (Aves: Pelecanidae): Five decades with ENSO, dynamic nesting, and contemporary breeding status in the Gulf of California

Daniel W Anderson,Rosalía Avalos-Tellez,Hugo Moreno-Prado,Lorayne Meltzer,Carlos R Godínez-Reyes,Jesus Trejo-Ventura,Enriqueta Velarde,Franklin Gress,David Ramírez-Delgado,Lindsay Adrean,Thomas Bowen

doi:10.7773/cm.v43i1.2710

Abstract

The California Brown Pelican subspecies (Pelecanus occidentalis californicus) was removed from the US endangered species list in 2009, along with the entire species of Brown Pelican throughout North America. The Gulf of California subpopulation within the entire metapopulation (= subspecies) comprises the majority of nesting (~76% of P. o. californicus). The US classifications were based on pollution effects in the Southern California Bight (SCB) during the early 1970s; official listing-recognition in Mexico (NOM-059-SEMARNAT-2010) occurred in 2010 and it continues. Unfortunately, Brown Pelican conservation across the US/Mexico border has been largely uncoordinated. Recent declines in the SCB subpopulation are not well-documented, whereas representative subpopulations in the Gulf of California have received continual study since the US listing. Until the early 2000s, Gulf pelican breeding populations changed little. El Niño/Southern Oscillation continues to be a major factor driving annual pelican breeding intensity and success, with a slightly weaker effect to the north. Nest attempts (NA) in the southern Midriff zone and to the south of our monitoring zone have declined in the last decade, in especially extreme and unprecedented ways in a period of unusual warming in the last 3 years (2014–2016), termed by some as the “Blob”. Other factors (such as human disturbance and commercial fishing) have likely exacerbated recent warming effects in some areas. Recent data also suggest the pelican is in a process of minor range-shifting toward the northern Gulf, and there are no definitive indications of a recent NA decline in that zone. Monitoring over the entire range, past 2016, will be important to determine whether populations have begun a long-term decline or will recover to normal baseline levels. The health of pelican populations is an important indicator of overall ecological health in the Pacific region and not an isolated phenomenon.

Highlights

International perspectives on California Brown Pelican conservation: A backgroundEndangered species and other listing processes in the UnitedStates and MexicoIn the United States (US) the Brown Pelican species (Pelecanus occidentalis) was officially classified “endangered” under the Endangered Species Act (ESA) of 1973 (Gress and Anderson 1983)
We further examined pelican breeding efforts for additional colonies south of our Comisión Nacional de Áreas Naturales Protegidas (CONANP) monitoring area, for 2 reasons: (1) it had already been demonstrated that El Niño/Southern Oscillation (ENSO) effects are more pronounced to the south in the Gulf (Anderson et al 2006), and (2) some colonies south of our study area are closest to the highest industrial, trawling fishery activities, which potentially affect seabirds such as the pelican (Velarde et al 2015a)
We found a close relationship (P < 0.001) between the breeding effort of pelicans at San Luis Island (SLU) and nearby Cholluda Island (CHL) (Fig. 3a), as well as Piojo Island (PIO) and San Lorenzo Archipelago (SLA) (P < 0.01) (Fig. 3b)

Summary

Introduction

International perspectives on California Brown Pelican conservation: A backgroundEndangered species and other listing processes in the UnitedStates and MexicoIn the United States (US) the Brown Pelican species (Pelecanus occidentalis) was officially classified “endangered” under the Endangered Species Act (ESA) of 1973 (Gress and Anderson 1983). Pollution-caused reproductive failures in the mid-1960s and early 1970s (Keith et al 1971, Risebrough et al 1971, Risebrough 1972, Jehl 1973, Anderson and Gress 1981, Gress and Anderson 1983, Gress 1995, and references therein) resulted in the federal and state of California endangered species status in 1970 and 1971 (Leach and Fisk 1972, California Fish and Game Commission 1981) This classification applied to all subpopulations within the range of the subspecies, the California Brown Pelican Pelecanus o. californicus, along with the remainder of the Brown Pelican total species, after extensive review and preceded by a long delay (Table 1) (see recent reviews of the recovery by USFWS 2008 and Burkett et al 2007), was removed

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