Breeding biology of the Atlantic Least Tern (Sternula antillarum antillarum) in a colony of the south of the Gulf of Mexico: new perspectives for its threat status

César González Zuarth,Adriana Vallarino,Alfonso Vázquez Botello

doi:10.1007/bf03544361

Abstract

Although the Atlantic Least Tern ( Sternula antillarum antillarum ) faces the same threats that caused the California Least Tern ( S. antillarum browni ) and the Interior Least Tern ( S. antillarum athalassos ) to be declared threatened, it is considered as “Least concern” globally, mainly because of its wide geographic distribution. However, many populations are threatened and the conservation status of several others is unknown. We evaluate, for the first time, the breeding biology of a colony of Atlantic Least Terns in the southern Gulf of Mexico. During the 2010 breeding season we censused and analyzed some relevant breeding variables for the stability of a colony at Terminos Lagoon. The starting date of egg laying and breeding peak, the clutch size variation during the breeding season and the main causes of eggs loss are similar to those reported for other colonies of this species. However, we found that the size of first (A) and single (S) eggs did not change throughout the season, but second (B) eggs size decreased. The number of breeding pairs and its higher hatching success in comparison with other colonies allow us to affirm that the colony of the Terminos Lagoon must be taken into account in conservation programs of this species. These results will settle the basis to reconsider its threat status globally and to compare breeding parameters with other colonies from the region.

Highlights

Seabirds are one of the most threatened taxon globally, with more than 25% of the species listed in risk categories by the International Union for Conservation of Nature and Natural Resources - IUCN (Croxall et al 2012)
The 344 nests found in this study are equivalent to the 4.7% of the breeding pairs from Maine to Virginia, 17% of the 2000 pairs nesting on natural beaches in coastal South Carolina, Georgia, and north Florida (Jodice et al cited in Brooks et al 2013) and 15% of the 2250 breeding pairs estimated for the Caribbean (McGowan et al 2006)
Based only on its size, we can affirm that the colony of the Atlantic Least Tern in the Terminos Lagoon, is large enough to be taken into account in the management plans for the species

Summary

Introduction

Seabirds are one of the most threatened taxon globally, with more than 25% of the species listed in risk categories by the International Union for Conservation of Nature and Natural Resources - IUCN (Croxall et al 2012) This is mainly due to consequences of human activities like pollution, overfishing, egg collection for human consumption, loss of habitat, tourism, invasive species on the breeding grounds and global climate change (Croxall et al 2012). These threats have raised the need of monitoring. In some seabird species, clutch and egg size are diminishing through time when compared with long term data sets: i.e. Glaucous-Winged Gulls (Larus glaucescens: Blight 2011) and Atlantic Puffins (Fratercula arctica: Barrett et al 2012)

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