A Rocha Portugal Observatory Report 2009-2010

A Rocha Portugal Observatory Report 2009-2010 23
A STUDY OF THE KENTISH PLOVER, CHARADRIUS ALEXANDRINUS, IN THE RIA DE ALVOR
Andrew Cole
Introduction
The Kentish Plover, Charadrius alexandrinus, is a geographically widespread wader which breeds in a range
of different habitats (Cramp & Simmons, 1983). In Portugal there are an estimated 1,500 to 5,000 breeding
pairs with 1,000 to 4,400 individuals over-wintering (Burfield, et al., 2004). There have been recent declines
in Kentish Plover populations thought to be due to habitat changes and human disturbance. The declines
have caused some small subpopulations to disappear, such as in Northern Spain (Norte & Ramos, 2004;
Cramp & Simmons, 1983).
The breeding of the Kentish Plover has been studied in many different habitats; inland saline lakes, alkaline
grasslands, marshes and sandy beaches, although this last habitat has been studied less extensively (Norte
& Ramos, 2004). In Portugal, however, sandy beaches are the most important natural habitat for breeding
Kentish Plover, while salinas and fish farms are important man made habitats (Norte & Ramos, 2004;
Rufino, et al., 1984). An important proportion of Kentish Plovers in Portugal are also found in non-estuarine
habitats (Mendes, et al., 2008).
Different techniques have been used when estimating the number of Kentish Plovers in a given area,
ranging from the number of individuals to the number of pairs (Burfield, et al., 2004; Lorenzo & Emmerson,
1995). Because Kentish Plovers nest close together, territorial behaviour can be used to aid in the
estimation of the number of territories in an area (Cramp & Simmons, 1983). Territories can be counted in
addition to counting the number of individuals, juveniles and nests. This study was carried out on the Alvor
Estuary in southern Portugal and studied Kentish Plovers in three distinct habitats; sand dunes, salinas and
salt marshes. The study was undertaken during the 2010 breeding season and repeated the same
methodology carried out in 2004 and 2005 (Hayden & Heleno, 2004; Hayden & Heleno, 2005; Sousa, et al.,
2007). This facilitates across year comparisons, showing any long term trends in Kentish Plover numbers.
Methods
The research was carried out on the Alvor Estuary (37°07’57N 08°37’03W), a Natura 2000 site and the
location of many studies carried out by A Rocha Portugal. Observations were carried out in five locations
covering one marshland (Western Marsh, WM), two salt pans (Western Marsh Salinas, WMS; Odiaxere
Salinas, OS) and two dune systems (Meia Praia, MP; Alvor Praia, AP). These five sites had been previously
identified as encompassing the main habitat types of the estuary and the majority of known Kentish Plover
breeding areas (Hayden & Heleno, 2005; Sousa, et al., 2007).
Fieldwork was carried out in the breeding season in 2004, 2005 and 2010 following, as closely as possible,
the same methodology (Hayden & Heleno, 2004). Each of the five sites was visited every three weeks from
30 March to 13 July; a total of five visits in both 2004 and 2005, and six visits in 2010.
From a number of fixed observation points the location of every individual was recorded and the type of
behaviour observed, with behaviour grouped into: ‘apparently non-territorial’, ‘territorial’, ‘sitting on a
nest’, an ‘adult with juveniles’ and ‘juveniles’ on their own. ‘Juveniles’ or chicks were classified as very
young, medium age and close to fledging, based on size and moult progress as classified by Hayden and