Here's a story about oystercatchers to 'go figure'

A STORY of persistence paying off. Following my previous Nature Notes (July 4, 2024), I thought I would update you on the riverside oystercatcher nests that I have been watching.

You may remember that these were on pebble ‘beaches’, along the Wharfe, and had been ‘washed out’ by a sudden rise in river level, early in the season. However, each pair of oystercatchers laid another clutch of eggs and were incubating them.

When I next visited, the behaviour of the birds at the two nests furthest upstream was very different. If they saw me, instead of moving quietly away from the nest, as they had previously, they began calling loudly, energetically, and persistently. I guessed this was because the eggs had hatched.

Although the chicks are very well camouflaged for the environment, any movement would make them easier for predators to spot. So, a parent bird calling might have multiple purposes: i) to distract or dissuade a potential predator; ii) to tell the chicks to stay still or out of sight; and, iii) to educate the chicks about dangers in their world.

The third riverside nest site is the furthest downstream and it seems to have been subjected to extended disturbance, with people visiting what is usually a secluded place.

For several days, after the eggs at the other nests had hatched, the oystercatchers here were still incubating. Moreover, it was apparent that, between my visits, the disturbance had continued. A discarded beach toy was a new addition to the area. As the days went by, I began to lose hope, and wondered if disturbance had caused the eggs to be left unattended for too long.

Then, one morning, everything changed. My approach, along the path on the opposite riverbank, was now greeted by an alarm call. I retreated and viewed from behind some trees.

The oystercatcher settled and I could see that the eggs had hatched and it was looking after two chicks. At this time, things were looking very positive for these three riverside nests – but, unfortunately, much of this was about to change.

On subsequent visits I found the two ‘upstream’ nest sites deserted. On occasions a pair of adult birds was there, but there were no alarm calls and no sign of any chicks. My guess is these chicks had been predated.

So, surprisingly, at the time of writing, the only one of these nests that is successfully raising chicks is the one that had suffered the most disturbance. In the words of the famous naturalist Charles Darwin, “Go Figure!” (Well, OK, that might not be an exact quote – but I bet he must have had occasion to say something similar.)