Won’t grasses growing on the beach affect waders by reducing their feeding areas?
The effect on wading birds raking/dune and saltmarsh succession at Hoylake Beach – RSPB and CAWOS response
Currently, waders that feed at Hoylake feed on marine invertebrates that are exposed between tides. Since the green beach is above the intertidal zone, whether it is grassed or raked will not affect the available food supply of intertidal marine macroinvertebrates.. Further east, where the grasses are Spartina not Puccinellia, and tidal inundation still occurs, the argument that a vanishingly small c.0.01% of feeding habitat is covered could be made. However, it is also important to remember that coastal terrestrial invertebrates such as Amphipods and salt-tolerant Diptera within saltmarsh can be superabundant and make up a considerable part of the diet of species such as Curlew, Dunlin, Ringed Plover and Redshank. Providing a mosaic habitat is better in terms of providing greater food heterogeneity. Also, waders need roost sites, just as much as feeding sites. The Green Beach at Southport is an excellent comparison. It vegetated quickly and is still used for feeding, as well now being an important roost site for waders. In short, waders are not losing any habitat; they are gaining habitat.
In contrast, mechanical raking has been shown to significantly decrease the biomass of macroinvertebrates in multiple studies eg. [Gilburn 2012, Schooler 2019] This can be expected to have a seriously detrimental effect on wading birds using Hoylake if raking is resumed.
What do WeBS counts show in terms of waders using Hoylake?
Most arctic wader species are suffering catastrophic declines as a result of climate change affecting their breeding grounds, so any changes need to be viewed in that light. There is a lot of interchange between the Dee, Mersey, Alt, and Ribble Estuaries, and even other sites like the Wash, depending on tides states, exposed intertidal area, weather and localised disturbance. For this reason, WeBS counts are coordinated across the country and the site-specific effects are hard to establish. On the whole waders on the Dee are doing well, because of the mix of habitat mosaic and overall structure. See attached WeBS counts. Taking Hoylake in isolation from the rest of the Estuary, as wind-borne sand as opposed to water-borne silt, continues to be deposited, we can expect to see mudflats replaced with sand flats will alter the relative abundance of different marine invertebrates and we can expect this to have an effect on the balance of species that use Hoylake. Favouring the short-billed surface feeders such as Sanderling which mostly feed on tiny Hydrobia snails [Lourenço 2015], over longer-billed species such as Redshank which specialise in feeding on subsurface invertebrates. The development of a green beach will provide an increase in coastal terrestrial invertebrates.
Will the ongoing dune succession and green beach have any other benefits for wading birds?
Initially, the effect will be neutral. Birds use Hoylake beach as a high tide roosting site and their primary concern is to roost and conserve energy. They do use Puccinellia clumps as shelter from strong winds, but as a rule, they just need somewhere to sit undisturbed. Eventually, if the vegetated zone is wide enough, it may put sufficient distance between the roosting birds and potential human disturbance to have a significant benefit. Similarly, we can perhaps expect species such as Ringed Plover to breed on North Wirral once again. There are a few pairs on adjacent coasts [Prater 1988]
Several other species including Snow Bunting, Reed Bunting, Rock Pipit, Meadow Pipit, Linnet, Brent Goose and White and Yellow Wagtails have been observed feeding in the new habitat at Hoylake. Using the green beach at Southport as a likely predictor of the value to a wide range of species, should the natural accretion process we allowed to continue, it is highly likely that there will be significant benefits to bird populations.
Graham Jones, RSPB Site Manager, Dee Estuary Nature Reserves. Jane Turner, Cheshire and Wirral Ornithological Society/BTO Surveyor for Hoylake and Meols tetrads.
References
British Trust for Ornithology Wetland Bird Survey Online Report
References
Gilburn, A Mechanical grooming and beach award status are associated with low strandline biodiversity in Scotland Estuarine Coastal and Shelf Science 107:81–88 https://www.researchgate.net/…/257105673_Mechanical…
Lourenço et al Foraging ecology of sanderlings Calidris alba wintering in estuarine and non-estuarine intertidal areas 2015 Journal of Sea Research, 104 33-40. https://www.researchgate.net/…/279738040_Foraging…
Prater, A.J Ringed Plover Charadrius hiaticula breeding population of the United Kingdom in 1984, Bird Study 36, 154-160 https://www.tandfonline.com/…/10.1080/00063658909477020Schooler, N.K., et al , No lines in the sand: Impacts of intense mechanized maintenance regimes on sandy beach ecosystems span the intertidal zone on urban coasts Ecological Indicators 106 (2019) 105457 https://par.nsf.gov/servlets/purl/10123258#birds