Kees Koffijberg. Living on the edge: breeding birds on Wadden Sea salt marshes

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1 Photo: Harvey van Diek Wadden Sea Day, 29 August 2013 Living on the edge: breeding birds on Wadden Sea salt marshes Kees Koffijberg Contact: kees.koffijberg(at)sovon.nl Sovon Vogelonderzoek Nederland, Nijmegen NL & Joint Monitoring Group for Breeding Birds (JMBB)

2 2 / 21 - Introduction Wadden Sea Day Wilhelmshaven, Birds and salt marshes Feeding habitat for staging herbivores...and specific passerine bird species Harvey van Diek Habitat use Barnacle Goose Data: Koffijberg & Günther 2005 / Wadden Sea Ecosystem 20

3 3 / 21 - Introduction Wadden Sea Day Wilhelmshaven, Birds and salt marshes Roosting sites for species feeding on the intertidal mud flats Harvey van Diek / Koffijberg 2003 / Wadden Sea Ecosystem 20

4 4 / 21 - Introduction Wadden Sea Day Wilhelmshaven, Birds and salt marshes Breeding habitat for many breeding birds Harvey van Diek / >25% of NW-European breeding population in Eurasian Spoonbill, Avocet, Lesser Black-backed Gull, Gull-billed Tern and Sandwich Tern breed in the Wadden Sea Koffijberg et al / Wadden Sea Ecosystem 22

5 5 / 21 Biodiversity - Global perspective Wadden Sea Day Wilhelmshaven, Salt marsh breeding birds: generalists and endemics Harvey van Diek Avocet / Shelduck lynx editions Bay-capped Wren Spinetail (S.Am.) versus Harvey van Diek Oystercatcher / Common Tern Swamp Sparrow (N.Am.) Harvey van Diek Sandwich Tern roysephotos.com Seaside Sparrow (N.Am.) Greenberg & Maldonado 2006 / Studies in Avian Biology 32

6 6 / 21 Habitat perspective Wadden Sea Day Wilhelmshaven, Salt marshes as a refuge for farmland birds? Data: Sovon/CBS Breeding bird monitoring scheme (BMP) the Netherlands

7 7 / 21 Trends in numbers Wadden Sea Day Wilhelmshaven, Wadden Sea breeding birds in decline Data: TMAP data, JMBB 2013 / Progress report

8 8 / 21 Trends in numbers Wadden Sea Day Wilhelmshaven, and the rate of decline accellerates after 2000 Data: TMAP data, JMBB 2013 / Progress report

9 9 / 21 Regional trends Wadden Sea Day Wilhelmshaven, South West gradient: summary of national trends (N = 17 species that occur in all countries in relevant numbers) Data: JMBB 2013 / Progress report

10 10 / 21 Backgrounds Wadden Sea Day Wilhelmshaven, Why do so many birds decline? Low breeding success: many breeding birds in the Wadden Sea produce too few offspring to maintain population, as also shown by preliminary date of new TMAP parameter ( ) Number of study sites with more (green) or less (red) 0,35 fledged Oystercatchers / year in the Dutch Wadden Sea Number of study sites with more (green) or less (red) 0,40 fledged Eider / year in the Dutch Wadden Sea Data: Sovon / IMARES

11 11 / 21 Backgrounds - predation Wadden Sea Day Wilhelmshaven, Major issues: predation Often mainly operating at mainland salt marshes (mustelids, red fox,...), locally also barrier-free islands (e.g. hedgehog Norderney)... and often associated with vegetation, i.e. concealed breeding in high vegetation may contribute to higher hatching success (e.g. Thyen & Exo 2005, Maier et al. in prep.) Data: Thyen et al in Vogelwelt 126

12 12 / 21 Backgrounds - predation Wadden Sea Day Wilhelmshaven, Predators often come at night... Nest attendance in Redshank responds to risk of (nocturnal) predation: survival of adult versus survival of its clutch Nest attendance in Redshank in relation to breeding site on the salt marsh Data: Cervencl et al in J Ornithol 152

13 13 / 21 Backgrounds - predation Wadden Sea Day Wilhelmshaven, Risk of predation (i.e. increased facilitation of land predators) often not considered in management issues Noordpolder, Groningen Coast, May 2013 (project Kwelderherstel Groningen )

14 14 / 21 Backgrounds flooding risk Wadden Sea Day Wilhelmshaven, Major issues: flooding risk Mean risk of flooding at least once during the breeding season has increased since 1971 and will further increase in future (due to increased chance of storm surges during the breeding season) Data: van de Pol et al in Journal of Applied Ecology 47

15 15 / 21 Backgrounds flooding risk Wadden Sea Day Wilhelmshaven, Living on the edge...? Johan Krol Dries Oomen Breeding birds prefer elevated nest sites: elevation increases with increase of flooding risk (Linthorst-Homanpolder) (total sample N = 322 nests) Data: Sovon & NAM, Koffijberg et al / Sovon-rapport 2013/26

16 16 / 21 Backgrounds flooding risk Wadden Sea Day Wilhelmshaven, Risk of flooding differs in time and space (and between species) Risk of flooding during 10-year period: ranging from 0 (never) to 1 (every year) in relation to nest elevation and laying dates Data: Sovon & NAM, Koffijberg et al / Sovon-rapport 2013/26

17 17 / 21 Backgrounds management and vegetation Wadden Sea Day Wilhelmshaven, Major issues: management & vegetation (but see also next presentations) Different response of breeding birds to percent cover of tall vegetation (e.g. Elymus, Phragmites): General abundance + Avocet Ostercatcher +/= Redshank + Meadow Pipit + - Skylark + - Reed Bunting + Data: Mandema et al. submitted

18 Not classified Brackish marsh Grassland High marsh Low marsh Pioneer zone Not vegetated Not classified Brackish marsh Grassland High marsh Low marsh Pioneer zone Not vegetated Not classified Brackish marsh Grassland High marsh Low marsh Pioneer zone Not vegetated Density, territories/ha Density, territories/ha Density, territories/ha 18 / 21 Backgrounds management and vegetation Wadden Sea Day Wilhelmshaven, Large variation in densities in vegetation types Oystercatcher Redshank Meadow Pipit Breeding density (territories/ha) per vegetation type (TMAP classification) from 51 census areas along the mainland coast Wadden Sea NL Data: Sovon & NAM, Koffijberg et al / Sovon-rapport 2013/26

19 19 / 21 Backgrounds food availability Wadden Sea Day Wilhelmshaven, Major issues: food availability and quality Feeding habits of nonbreeding herbivores known in detail...but knowledge on food availability and quality for breeding birds poorly known grazed mown fallow Photo: Martin Maier / Univ. of Oldenburg

20 20 / 21 Backgrounds food availability Wadden Sea Day Wilhelmshaven, Food quality matters! Breeding Meadow Pipits go for larger prey items, e.g. large spiders, caterpillars... and more homogeneous habitat was preferred for feeding (not patchy sites) Data from M. Maier (manuscript) show that abundance of invertebrates is negatively correlated with their energy content Data: van Klink et al. submitted

21 21 / 22 Summary Wadden Sea Day Wilhelmshaven, To summarise Wadden Sea salt marshes are an important breeding habitat, but compared to the new world, no endemic (sub)species are involved Many species are in decline, salt marsh breeders and other species For some species, Wadden Sea might be a good alternative for farmland, but this is species-specific Main driver for declines seems poor reproduction, caused by predation and flooding (among others) Link between breeding densities and vegetation/management ask for long-term analyses We start to understand association between breeding densities and food supplies and it will be a challenge to continue

22 22 The End Wadden Sea Day Wilhelmshaven, Dilemma s of a salt marsh breeder Find suitable nesting habitat with high quality food Failed next year next try But well elevated, otherwise risk of flooding Better off at high marsh, when not those predators were after me Oh no, Horses!