In a previous Nature Notes (July, 2023) I described the Oystercatchers that nest along the Wharfe. Their red/orange bills and eyes, pink legs, and pied plumage, mean they are an easy bird to identify visually, and anyone who has spent time near the river will most likely have heard their piercing calls. However, when they want to, e.g., when nesting, they can keep a surprisingly ‘low profile’ – and that is the theme of these Nature Notes.

The stony beaches along the banks of the river Wharfe - ones that are tucked out of the way and aren’t adjacent to a footpath – are usually the chosen breeding location for a few pairs of Oystercatchers – and this year has been no different. They select a spot some way up from the water, to make allowance for rises in river level. They also prefer to keep a little distance from the vegetation at the back of the ‘beach’, perhaps to avoid predators and give better line of sight to anything approaching the nest.

Their nests take the form of a simple scrape, or scoop, amongst the stones. Into this, the female will lay three eggs – give or take. Once laying is complete, both parents take turns incubating (this YouTube video shows Oystercatchers swapping nesting duties: https://youtu.be/DcRSW2kuq2U?si=tAt92WxuxhM39Ot). From that point in time the birds need a window of approaching four weeks, without flooding, predation, or disturbance, until the eggs hatch and their semi-precocial chicks are able to make their way to nearby vegetation. The chicks will spend much of their time hiding and feeding there over the coming weeks, albeit with continued parental support in the form of providing food, brooding (until they can regulate their own temperature), and protection from predators.

Oystercatchers must have great confidence in the extent to which their eggs blend in to the surrounding environment. If people are in the vicinity of the nest – even at quite some distance and on the opposite riverbank - a typical response is for the ‘sitting’ bird to quietly rise and move away, leaving the eggs behind. Sometimes this is accompanied by it feigning feeding behaviours or preening, perhaps to signal nonchalance (see photograph, “Nothing to be seen here, mate, move along”). They may even feign incubating in a different location. Oystercatchers have a range of defence behaviours they can deploy, including alarm calls, feigning injury, and attacking/mobbing. However, walking quietly away from their nest seems to be frequently used in the presence of potential terrestrial predators.

wharfedale-nats.org.uk