Blue-footed Booby Population Analysis

Blue-footed Booby Population Analysis
CURRENT

PROJECT:

Blue-footed Booby Population Analysis

PARTNER:

Dr. David Anderson, Wake Forest University

STATUS:

First study conducted in 2011/12; follow-up study in progress (June 2017-May 2018)

 

Blue-footed booby pair

Blue-footed booby pair © Shelale Savash.

 

Background

Blue-footed boobies (Sula nebouxii) are iconic birds that contribute to the biodiversity of the Galapagos Islands. Over the years, concerns that the booby population was declining on an island-wide scale prompted the need for periodic, comprehensive studies to assess the population size, understand the cause of the decline, and inform necessary conservation actions. Initial research in 2012 for this project confirmed the decline in population and suggested that it may be closely tied to a decline in clupeid fish, especially sardines, in the boobies’ diet.

Project data from 2012 suggest that the decline may be long-term; however, further data collection was needed to provide sufficient evidence to conclude that this is a permanent condition and not just a normal fluctuation that may last several years. Due to many anecdotal sightings of juveniles blue-footed boobies early in 2017, the first evidence of substantial reproductive success this century, it was decided to do a follow-up survey this year (beginning in June 2017) in order to provide a second quantitative estimate of population size, and to evaluate recent reproductive activity.

Project Overview

In May 2011, seabird biologists Dave Anderson of Wake Forest University, Kate Huyvaert of Colorado State University, and Ecuadorian Master’s degree student David Anchundia (now of the Charles Darwin Foundation) began the first comprehensive survey of blue-footed booby distribution and population dynamics in the Islands with support from Galapagos Conservancy, Galapagos Conservation Trust, and Swiss Friends of Galapagos. This effort came in response to concerns of several long-time Galapagos observers that this iconic species seemed to be declining in numbers. Traditional breeding sites seemed to be largely unattended and without successful nesting; indeed, the large colony of hundreds of nests at Anderson’s research site on Española Island had been essentially unused since 1997.

The research team completed four rounds of intensive searches of major breeding colonies in Galapagos at four-month intervals in 2011, followed by a coastal survey around the entire Archipelago (except several northern islands) in 2012. In both years, few juvenile birds were observed (<100), indicating that little breeding was occurring. The preliminary estimate of the adult population was 6,000-8,000 birds, compared to an estimated 20,000-30,000 breeding birds estimated in the 1960s and 1970s. The contrast between even these admittedly loose numbers suggested a substantial decline in population size.

Dr. Anderson suspected that the lack of food was behind the failure of blue-footed boobies even trying to breed. Previous work on Española had shown that successful breeding occurs when blue-footed boobies have access to sardines. The researchers published a paper from this project in the online journal Avian Conservation and Ecology in 2014 confirming the decline in population, and suggesting that it may be closely tied to an observed decline in clupeid fish, especially sardines (Sardinops sagax), in the boobies’ diet.

In June 2017, researchers Anderson, Huyvaert, and Anchundia began a second study to repeat the previous population count and collect data on the boobies’ diet, using the same methods as their previous study, again with support from Galapagos Conservancy. Their efforts will: 1) allow development of a time series of this population’s sizet, 2) provide an estimate of the degree of successful breeding among blue-footed boobies in Galapagos, and 3) evaluate the possibility that sardines have become available in the central archipelago.

This work is in part funded by The Blue Feet Foundation, an ambitious endeavor started by two young brothers in Massachusetts, who have donated $17,000 (as of June 2017) to Galapagos Conservancy since 2016 from the sale of their blue-footed booby socks.

Publications

In April of 2014, Dr. Anderson and his team published a peer-reviewed research paper in the online journal Avian Conservation and Ecology titled Chronic lack of breeding by Galapagos Blue-Footed Boobies and associated population declinewhich supports his case that the reduction in the Blue-footed Booby population may be closely tied to a decline in clupeid fish, especially sardines (Sardinops sagax).