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Plovers under pressure: Kentish Plovers in southern Portugal

An ominous trend

Alvor Estuary seen from the headland
The Alvor Estuary

The Kentish Plover Charadrius alexandrinus is an attractive small plover that has been seen widely around the world. It was first recorded in the English county of Kent where it once bred but is now no more than a rare migrant. There has been a dramatic decline in world populations of this species, largely because of the loss of the coastal wetlands that are its main breeding habitat.

In the Alvor Estuary of southern Portugal, a considerable breeding population of Kentish Plovers has been found and studied by A Rocha Portugal from Cruzinha, their field study centre. Despite the fact that only a few coastal wetlands are left in Portugal, the number of breeding Kentish Plovers is still relatively high, with a population estimated at between 1,100 and 1,600 pairs, representing perhaps 4% of the European population. In the Alvor Estuary, the last remaining wetland in the western Algarve, there are estimated to be at least 54 pairs of breeding Kentish Plovers. Four sites, including two areas of sand dunes, a salt marsh and some former saltpans, are annually occupied by breeding birds.

Studying nesting and hatching

A Rocha teams first started to investigate the breeding Kentish Plover populations in 1992. From 1996 onwards a number of major studies on these birds have been carried out during the breeding season by students under the supervision of Mark Bolton. These studies were designed to find out more about the factors that influence Kentish Plovers in selecting a nest site and which determine hatching success. One of the most detailed studies was in 1999, by Petra Crofton-van Rijssen. All the nesting sites found (141 in total) were surveyed and monitored at least once a week throughout the breeding season. The surveys investigated the nest site selection and the hatching success in relation to various environmental factors, such as the distance to the nearest feeding ground, the density and height of any vegetation cover, the distance to the nearest roads, the extent of predator presence and the degree of human activity nearby. One of the purposes of the study was to apply the results in order to protect and manage the breeding sites better.

The study concluded the failure of the plovers to successfully hatch egg clutches was mainly due to predation by other birds, notably the Yellow-legged Gull Larus michahellis. Human leisure activities, such as beach recreation and motorcycling, seem to have a smaller effect, largely because the dune areas where the plovers breed are relatively undeveloped and therefore attract only limited numbers of tourists. Human factors are however important; both sand excavation for building and the artificial flooding of the marsh cause the loss of egg clutches. A further factor is natural change; because Kentish Plovers prefer bare surfaces for nesting, the spread of vegetation over former areas of open dune and marsh has gradually reduced the area available for breeding.

This study also asked various other questions such as

  • Are the methods used to search for egg clutches and to predict the stage of incubation of the eggs accurate? Answer: probably yes, but improved techniques may be possible.
  • Does studying nesting sites increase the chance of a nest being preyed on by birds or mammals? Answer: here, almost certainly not.
  • Can placing dummy nests with foul tasting eggs in a nesting area of Kentish Plovers deter predators? Answer: at best, only for a short time and not long enough to make a difference.
  • Do Kentish Plovers deliberately choose to nest next to Little Terns Sterna albifrons in order to benefit from the terns' aggressive attitude to predators? Answer: probably yes, but as the terns' behaviour seems to draw the attention of predators to nest sites it doesn't seem to do much overall good.

Their future in our hands

Petra Crofton with a Kentish Plover chick
Petra and a Kentish Plover chick
Some of the threats to breeding success of the Kentish Plover in the Alvor Estuary can be managed more easily than others. While control of predation by Yellow-legged Gulls is hardly feasible, there are several human activities that directly influence the selection of nest sites and breeding success and these should be managed. For example, the artificial flooding of the marsh and the excavation of sand for construction work should be controlled so that they occur outside the breeding season.

The control of human activity levels in the dunes is also necessary to keep the area suitable for breeding plovers. High levels of human activity, such as people walking through the dunes or using the beach, cause significant disturbance to the birds when nesting and feeding, and can cause both eggs and chicks to be trampled. In the Alvor dunes, breeding colonies of Kentish Plovers are only found in the more isolated and undeveloped areas. Three things are needed to safeguard the Kentish Plover population in the Alvor estuary:

  • Limits on access to the nesting areas, at least during the breeding season.
  • Restrictions on the construction of beach facilities for tourists.
  • The immediate protection of certain dune areas during the breeding season. Given that the Alvor dunes are within a proposed Natura 2000 protected area under the European Union Habitats Directive legislation, some sort of legal protection seems essential.

These suggestions may make it seem that matters are a stark choice between conservation or human interest; between plovers or profits. The reality is that a good deal of cooperation is possible. So, for instance, if sand excavations were carried out just before the nesting season in March, they could have a positive impact on breeding by creating bare areas suitable for nesting. And one solution to increase the area of bare sand suitable for nesting is to have sheep, goats or cows graze the area to reduce the spread of vegetation.

Nevertheless unless some action is taken Kentish Plover populations in the Alvor Estuary will almost certainly decline dramatically. People and birds can live together but it needs work to make it happen. A Rocha Portugal is currently involved with a number of initiatives to ensure that these birds, and their nesting sites, are protected.

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Further details on this work and on the continuing studies on the Kentish Plover populations of the Alvor can be obtained from portugal@arocha.org.

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