Wintering waders on the Portuguese mainland non-estuarine coast: results of the 2009–2011 survey

Miguel Lecoq1,2, Pedro M. Lourenço2*, Paulo Catry1,2, Joana Andrade3 & José Pedro Granadeiro4

1 Eco-Ethology Research Unit, ISPA, Rua Jardim do Tabaco 34, 1149-041 Lisbon, Portugal 2 Museu Nacional de História Natural e da Ciência, Universidade de Lisboa, Rua da Escola Politécnica 58, 1250-102 Lisbon, Portugal 3 Sociedade Portuguesa para o Estudo das Aves (SPEA), Avenida João Crisóstomo, n.º 18 – 4.º Dto.1000-179 Lisbon, Portugal 4 Centro de Estudos do Ambiente e do Mar (CESAM)/Museu Nacional de História Natural e da Ciência, Universidade de Lisboa, Rua da Escola Politécnica 58, 1250-102 Lisbon, Portugal * Corresponding author: [email protected]

Lecoq, M., Lourenço, P.M., Catry, P., Andrade, J. & Granadeiro, J.P. 2013. Wintering waders on the Portuguese mainland non-estuarine coast: results of the 2009–2011 survey. Wader Study Group Bull. 120(1): XX–XX.

Keywords: waders, shorebirds, non-estuarine coast, survey, Portugal

Population estimates of wintering waders on the non-estuarine European coasts are largely based on extrapolated data from relatively small stretches of coast. In Portugal, the previous and only national estimate of waders wintering on the non-estuarine coast was based on just 7.3% of the coastline. In this study we carried out the first survey of waders wintering on almost the whole of the non-estuarine coast of Portugal, in order to improve knowledge on their abundance and distribution and to set a baseline for interpreting future population trends. The majority (98.5%) of the 198 5 × 5 km UTM squares, covering 1,096 km of coastline, were counted by observers walking along the shore within ±3 h of low tide during the 2009/2010 winter. 6,866 waders, of 13 species, were counted and we estimate the entire Portuguese population at 7,175. Sanderling (2,897–3,027), Ruddy Turnstone (2,191–2,289) and Kentish Plover (581–607) were the most abundant species. Highest wader numbers were found on the north and central (mainly around the Tagus estuary) coasts. The non-estuarine coast holds a significant proportion of the Portuguese winter populations of Sanderling (83.6%), Purple Sandpiper (83.3%), Ruddy Turnstone (80.1%), Whimbrel (33.5%), Kentish Plover (17.0%), Common Sandpiper (16.0%) and Eurasian Oystercatcher (15.7%). The study also highlights the international importance of the Portuguese non-estuarine coast for wintering Sanderling, Ruddy Turnstone and Kentish Plover, as the counts for these species represent ≥1% of the relevant biogeographic populations.

INTRODUCTION often without easy access (Rehfischet al. 2008). Therefore for most countries estimates of non-estuarine wader populations At high latitudes the majority of wader species undergo long have been based on extrapolations from relatively small-scale migratory flights between breeding and wintering locations. surveys (Rehfisch et al. 2008), and this is also the case for Most of the latter are estuarine wetlands, with individuals Portugal (Mendes et al. 2008). of different species congregating in large numbers in a few Located in the East Atlantic Flyway, Portugal supports major sites (van de Kam et al. 2004). While these areas sup- important numbers of several waders in winter and during port the bulk of wader populations (Delany et al. 2009), and migration (Alves et al. 2011, Catry et al. 2011, Delany et have been the focus of most wader research, the non-estuarine al. 2009). In winter, the Portuguese non-estuarine coast is coasts have also been shown to support important numbers estimated to hold internationally important numbers of Kent- of several species (Burton et al. 2008). ish Plover Charadrius alexandrinus, Sanderling and Ruddy During winter, the non-estuarine coasts of Europe hold Turnstone, as well as smaller numbers of six other species, but an important proportion of the biogeographic populations the survey on which these data are based covered just 7.3% of Common Ringed Plover Charadrius hiaticula (54%), of the coastline of the country (Mendes et al. 2008). Apart Purple Sandpiper Calidris maritima (34%), Sanderling from that study and the survey reported here, only very small Calidris alba (31%), Ruddy Turnstone Arenaria interpres parts of the Portuguese non-estuarine coast have been studied (24%) and Eurasian Oystercatcher Haematopus ostralegus in detail (Catry et al. 1992). (15%), and a total of 26 wader species (Burton et al. 2008). In an effort to improve upon earlier studies, and to bet- Populations on non-estuarine coasts seem to be very sensitive ter understand the importance of the non-estuarine wader to climate change (Rehfisch et al. 2004), emphasizing the populations of Portugal in the context of the East Atlantic need to monitor future changes in numbers and distribution. Flyway, we organised a new, large-scale survey that took However, monitoring effort in most countries has been very place ­during 2009–2011 covering the entire Portuguese limited, mostly due to the logistical difficulty of covering non-estuarine coast. Here we describe the results of this coasts that stretch for hundreds or thousands of kilometres, survey in detail. Wader Study Group Bulletin 120(1) 2013

METHODS 1,000 m. This length included all piers, jetties and sea walls. The length of the Portuguese non-estuarine coastline was Portugal has a long coastline in relation to its size; a coast that measured as 1,096 km. is almost entirely open and exposed, but relatively diverse, Although the survey covered a very high proportion of the including long stretches of sandy beaches, low rocky shores, Portuguese non-estuarine coast, providing a rather precise steep cliffs with small beaches, barrier islands and a few large figure for the wintering population of each species, we also estuarine wetlands. The tidal regime is semi-diurnal with am- estimated the total population by extrapolation, assuming the plitudes that vary in the range 2–4 m (Andrade et al. 2002). 4.3% of the coast that was impossible to count had the same The Portuguese non-estuarine coast (excluding islands) average number of each species per kilometre as the 95.7% was divided into 198 5 × 5 km UTM squares and the vast that was surveyed. majority of these squares (~96%) were visited in the winter To put the results into their broader context, we make of 2009–2010, between 5 Dec and 14 Feb. The few remain- comparisons with available data for the non-estuarine coasts ing squares were visited the following winter (2010–2011) of other European countries (Burton et al. 2008) and data between 10 Dec and 23 Feb. Ninety-six observers participated from the Portuguese Institute for Nature Conservation and in the survey. Forests (ICNF) for Portuguese estuarine wetlands (ICNF During each visit, an observer walked the entire coastline unpubl. data). within the designated square, counting all waders seen on the ground, including any that took flight. Inaccessible areas, RESULTS such as cliffs, rocky shoals or private piers, were counted from vantage points and, in the few cases where parts of the A total of 6,866 waders, of 13 species, were counted on the coastline were impossible to survey, the observer estimated Portuguese non-estuarine coast (Table 1). This extrapolates the proportion of coastline that was covered in the square. 7,175 including the 4.3% of coast that could not be surveyed. Most squares (83%) were fully surveyed, while the remain- The most abundant species were Sanderling (2,897 counted, der were 20–95% covered. Overall, 95.7% of the coast was 3,027 estimated for the whole coast by extrapolation), Ruddy surveyed in the study. Turnstone (2,191–2,289) and Kentish Plover (581–607). All counts took place in the period within ±3 h of low tide The counts for Sanderling and Ruddy Turnstone represent to minimize any bias caused by different tide levels, and only >1% of the relevant biogeographic populations, and that for on days of favourable weather and sea conditions to ensure Kentish Plover almost 1% (Table 1). These three species both the safety of the observer and good visibility. Three were also the most widespread, occurring in 30–60% of the squares with extremely high cliffs and difficult visibility from surveyed squares. Another six species were present in >10% the top were surveyed from an inflatable boat. of squares: Whimbrel Numenius phaeopus (21%), Common For a better comparison between squares, count data were Ringed Plover (15%), Common Sandpiper Actitis hypoleucos converted into numbers per kilometre of coast, using the (15%), Eurasian Oystercatcher (13%), Grey Plover Pluvialis total length of the coastline in each square, as determined squatarola (12%) and Dunlin Calidris alpina (10%). Another from aerial photography (Google Earth) from an altitude of four wader species were found in <2% of squares.

Table 1. Numbers of waders counted in winter on the non-estuarine coasts of Portugal during 2009–2011 and their international significance. Species Number1 Percent2 1% level3 Relevant flyway population(s)4 Eurasian Oystercatcher Haematopus ostralegus 163–170 0.02–0.02 10,200 1,020,000 H. o. ostralegus Eurasian Golden Plover Pluvialis apricaria 1–1 0.00–0.00 16,800 930,000 P. a. altifrons (Iceland) 500,000–1,000,000 P. a. altifrons (N Europe) Grey Plover Pluvialis squatarola 91–95 0.04–0.04 2,500 250,000 P.s.squatarola (E Atlantic) Common Ringed Plover Charadrius hiaticula 285–297 0.39–0.41 730 73,000 C. h. hiaticula Kentish Plover Charadrius alexandrinus 581–607 0.88–0.92 660 62,000–70,000 C. a. alexandrinus (E Atlantic and W Mediterranean) Bar-tailed Godwit Limosa lapponica 1–1 0.00–0.00 1,200 120,000 L. l. lapponica Whimbrel Numenius phaeopus 88–92 0.01–0.01 9,500 600,000–750,000 N. p. islandicus 190,000–340,000 N. p. phaeopus (NE Europe) Common Sandpiper Actitis hypoleucos 50–52 0.00–0.00 17,500 1,500,000–2,000,000 (N, C and W Europe) Ruddy Turnstone Arenaria interpres 2,191–2,289 1.46–1.53 1,500 100,000–200,000 (NE Canada and Greenland) Red Knot Calidris canutus 17–18 0.00–0.00 4,500 450,000 C. c. islandica Sanderling Calidris alba 2,897–3,027 2.41–2.52 1,200 120,000 C. a. alba (E Atlantic) Purple Sandpiper Calidris maritima 5–5 0.01–0.01 1,000 20,000–30,000 C. m. maritima (NE Canada and NE Greenland) 50,000–100,000 C. m. maritima (N Europe and W Siberia) Dunlin Calidris alpina 496–518 0.04–0.04 13,690 1,330,000 C. a. alpine 3,300–4,100 C. a. schinzii (Baltic) 23,000–26,000 C. a. schinzii (British Isles) 1 The first figure is the number actually counted along 95.7% of the coast; the second is the number estimated by extrapolation for the whole coast. 2 This is the count and estimate expressed as a percent of the relevant flyway population. 3 This is 1% of the relevant flyway population according to Delanyet al. (2009). 4 These are the populations within the East Atlantic Flyway part of which does or might winter in Portugal (Delany et al. 2009) which were used to calculate the 1% level. Lecoq et al.: Wintering waders on Portuguese non-estuarine coast: survey 2009–2011

Fig. 1. Linear density (mean number per km) of Sanderlings, Ruddy Turnstones and Kentish Plovers, the three most abundant wader species, and total waders along the non-estuarine coast of Portugal in winter during 2009–2011. Here the coast is divided into 10 sub-sections of the coast, each comprising roughly 20 UTM squares.

The results show that wader abundance is not evenly (Fig. 1), being particularly important for Whimbrels and spread along the coast. Highest numbers were found in the Common Sandpipers. northern and central portions of the coast (Fig. 1), the latter When the numbers of waders counted along the non- being roughly centred on the mouth of the Tagus estuary, estuarine coast of Portugal are compared with those found which is the largest and most important estuarine wetland in the country’s estuarine wetlands, it appears that the non- for waders in Portugal. The abundance of most individual estuarine coast supports most of the wintering populations of species shows a similar pattern. Generally the southern half Sanderlings (83.6%), Purple Sandpipers (83.3%) and Ruddy of the country was found to support lower numbers of wad- Turnstones (80.1%), about a third of the population of Whim- ers, although some stretches of the south-west coast and brels (33.5%) and substantial proportion of the populations of some restricted parts of the south coast, around the Ria For- Kentish Plovers (17.0%), Common Sandpipers (16.0%) and mosa coastal lagoon, also held comparatively high numbers Eurasian Oystercatchers (15.7%)(Table 2). Wader Study Group Bulletin 120(1) 2013

Table 2. Estimated number of waders wintering on the non-estuarine coast of Portugal during 2009–2011 compared with the mean number (±SE) wintering on Portuguese estuarine wetlands during 1989–2009 based on 16 mid-winter (January) counts (ICNF unpub. data). Species Non-estuarine coast Estuarine wetlands ±SE Total % on non-estuarine coast Eurasian Oystercatcher 170 926±92 1,083 15.7% Eurasian Golden Plover 1 710±257 711 0.1% Grey Plover 95 6,413±508 6,508 1.5% Common Ringed Plover 297 3,743±430 4,025 7.4% Kentish Plover 607 2,946±436 3,572 17.0% Bar-tailed Godwit 1 2,938±330 2,939 0.0% Whimbrel 92 189±40 275 33.5% Common Sandpiper 52 270±59 324 16.0% Ruddy Turnstone 2289 578±108 2,857 80.1% Red Knot 18 614±198 632 2.8% Sanderling 3027 574±97 3,620 83.6% Purple Sandpiper 5 1±1 6 83.3% Dunlin 518 40,211±3,579 40,729 1.3%

DISCUSSION do not reflect true population trends. If, however, we compare the data for the few coastal sections covered in both 2000 and The data we present amount to by far the most extensive 2009–2011, we find considerable increases for most species wader survey that has ever been carried out along the non-es- and an overall increase of 92% in the total number of waders tuarine coast of Portugal. Previous efforts were either focused (Table 3). This suggests that broadly the number of wad- on limited sections of coastline (Catry et al. 1992, 2010), or ers wintering along the Portuguese non-estuarine coast has sampled only a small proportion of the coast (Mendes et al. increased over the last decade, but two species, Grey Plover 2008). This survey should be considered as the baseline for and Purple Sandpiper, show a declining trend. Moreover, all future monitoring in the region. Comparing our results with the survey that took place in 2000 (extrapolated from a coverage of 7.3% of the coastline; Mendes et al. 2008), there appears to be enormous varia- Table 4. Comparison of linear densities (means ±SE) of waders found on the non-estuarine coasts of Portugal, the Atlantic coasts tion in the numbers of most waders. Eurasian Oystercatcher of NW Europe (Sweden, Denmark, Germany, the Netherlands, and Common Sandpiper show large increases (+294% and Belgium, United Kingdom, Ireland, France and Spain; Burton et al. +308%), while Grey Plover and Purple Sandpiper show 2008) and the Mediterranean coasts of W (France, Italy and Croatia; declines (–83% and –82%). Sanderling, Whimbrel, Ruddy Burton et al. 2008). Here we include three species (Northern Lapwing Turnstone and Kentish Plover numbers decreased by 21–48%, Vanellus vanellus, Eurasian Curlew Numenius arquata and Common while Common Ringed Plover increased by 13%. These very Redshank Tringa totanus) that were not recorded in the 2009–2011 large changes and their opposing directions strongly suggest survey of the Portuguese coast but are among the ten most abundant that they result from biases in the sampling effort in 2000 and on the non-estuarine coasts of Europe. Species Portugal Europe Europe (Atlantic) (Mediterranean) Table 3. Changes in the numbers of waders counted in the same Eurasian Oyster- 0.15 25.7±16.6 0.00±0.00 sections of the Portuguese coast that were covered in 2000 (Mendes catcher et al. 2008) and in 2009–11. Eurasian Golden 0.00 1.61±1.13 0.00±0.00 Species 2000 2009–2011 Change Plover survey survey Grey Plover 0.09 1.07±0.47 0.04±0.04 Eurasian Oystercatcher 3 8 +167% Northern Lapwing 0.00 1.54±0.77 0.20±0.20 Eurasian Golden Plover 0 0 = Common Ringed 0.27 0.78±0.42 0.01±0.01 Grey Plover 41 19 –54% Plover Common Ringed Plover 18 88 +389% Kentish Plover 0.60 0.00±0.00 0.05±0.01 Kentish Plover 72 114 +58% Bar-tailed Godwit 0.00 1.09±0.68 0.00±0.00 Bar-tailed Godwit 0 1 + Whimbrel 0.07 0.02±0.02 0.00±0.00 Whimbrel 8 12 +50% Eurasian Curlew 0.00 2.12±0.74 0.68±0.59 Common Sandpiper 1 2 +100% Common Redshank 0.00 0.71±0.31 0.01±0.01 Ruddy Turnstone 307 506 +65% Common Sandpiper 0.04 0.06±0.06 0.03±0.01 Red Knot 0 0 = Ruddy Turnstone 2.05 3.80±1.86 0.08±0.08 Sanderling 277 627 +126% Red Knot 0.01 15.17±14.61 0.00±0.00 Purple Sandpiper 2 0 –100% Sanderling 2.99 3.41±1.39 0.17±0.17 Dunlin 0 23 + Purple Sandpiper 0.00 0.68±0.26 0.01±0.01 Total waders 729 1,400 +92% Dunlin 0.40 14.54±10.55 0.17±0.14 Lecoq et al.: Wintering waders on Portuguese non-estuarine coast: survey 2009–2011

Purple Sandpiper numbers are also lower compared with thanks are due to the regional coordinators, Maria Dias, various other counts carried out in small sections of the coast Alexandre Leitão, Paulo Tenreiro, Paulo Travassos, Thys between the 1970s and the early 1990s, when the wintering Valkenburg, Isabel Fagundes and Joaquim Teodósio. Paulo population of the whole Portuguese coast was estimated at Cardoso and Maria Dias provided important help with GIS. “several dozen” (Catry et al. 2010). Portugal is on the edge of We would also like to thank the Portuguese Institute for the Purple Sandpiper’s wintering range (Delany et al. 2009) Nature Conservation and Forests (ICNF) for providing un- so it is perhaps not surprising that their numbers fluctuate at published data from estuarine wetland counts. We are grateful a low level. to José Alves for his review of our draft paper. 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