Utilisation of intertidal mudflats by the Dunlin Calidris alpina in relation to microphytobenthic biofilms

Abstract

International audienceThe small-scale spatial distribution of Dunlin Calidris alpina staging and wintering in Bourgneuf Bay (France) was investigated on two different mudflats colonized by either epipsammic- or epipelic-dominated microphytobenthos assemblages. Shorebird counts were conducted monthly at ebb tide from October 2011 to May 2012 and from November 2012 to May 2013. Multiple linear regressions followed by hierarchical partitioning of variance showed that microphytobenthos biomass was not a significant factor to explain Dunlin densities. However, on epipelic-dominated mudflats, Dunlins did not show their typical ‘‘tide follower’’ behaviour and instead significantly selected the highest microphytobenthos biomass zones. The biomass of a gastropod predator of an important local Dunlin prey, Retusa obtusa, was negatively correlated with Dunlin densities. This paper provides new suggestions in the ways that biofilms on mudflats affect small shorebird foraging

Growth and biochemical composition of a microphytobenthic diatom (Entomoneis paludosa) exposed to shorebird (Calidris alpina) droppings

“…Interestingly, it was also shown recently in the same mudflats that Dunlins seem to feed preferentially in zones exhibiting high microphytobenthic biofilm concentrations (Drouet et al, 2015). This suggests that in this bay there is a strong interaction between Dunlins and microphytobenthic biofilms.…”

Shorebirds Affect Ecosystem Functioning on an Intertidal Mudflat

“…Use of the mid and upper shore at low tide by C. alpina, despite often being a 'tide follower' (Granadeiro et al, 2006), may have been driven by the visual cues of MPB communities on the mudflats, either as a cue for the presence of invertebrate prey or to feed upon MPB directly (Hamilton et al, 2003;Drouet et al, 2015;Jimenez et al, 2015). C. alpina is an opportunistic feeder with a broad diet (Dierschke et al, 1999) using visual and tactile foraging cues (Drouet et al, 2015), and possibly exploited areas with high diatom biomass to maximize the breadth of feeding opportunity.…”

Taxon-Specific Habitat and Tidal use by Birds in an Oyster Culture Estuary

“…In the Fraser River Estuary, British Columbia, dunlin were found to follow the tide, whereas Western Sandpipers foraged in the upper intertidal where the microphytobenthos (MPB) was greatest (Jiménez et al 2015). In the presence of high MPB in Borgneuf Bay, France, dunlin were found to switch from tide-following behavior to foraging in high MPB areas (Drouet et al 2015). This suggests that the tide following behavior is plastic, and responds to resource availability for maximum foraging efficiency.…”

“…In the intertidal habitat mosaic studied here, habitats are exposed 0–2 times a day, depending on neap versus spring tides. Many shorebirds forage at the waterline (tide-following), where resources are emerging during an ebb tide and before infauna have burrowed down as water drains from sediment (Jiménez et al 2015), however, tide-following may be abandoned in particularly resource-rich environments (Drouet et al 2015). Given this, it is hypothesized that taxa that act as habitat-generalists will show strong tide-following tendencies.…”