Stonechats – Round 2 Wipeout

Following the successful fledging of 29 chicks from our first brood Stonechats on Dersingham Bog NNR, we hoped it would be followed with further success for our second broods. Typically, these broods tend to produce the highest numbers, both in terms of clutches laid, eggs hatched and fledged young, as the weather is usually more consistent and a lot warmer, with more food available for both adults and young.

Happy Valley - SC 6 eggs 2nd brood nest 2019As our volunteers steadily found all the second nests for our active Stonechat pairs, it soon became apparent that the females had laid some pretty large clutches. Of our 9 active pairs, 7 had laid clutches of 6 eggs, with the remainder on 5 eggs. We’ve had clutches of 6 eggs before but it’s usually only been 1 or 2 pairs at a time, so to have such a high proportion of big clutches right throughout the reserve was very promising.

As the incubation progressed to hatching, we were pleased to find that nearly all of the big clutches hatched in full, with very few unhatched eggs among them. So we planned the ringing excited at the thought that this time round we might have a record brood total, reserve-wide, with the possibility of 52 chicks due to be ringed.

Then the weather intervened.

In common with other areas of the country, Norfolk experienced a spell of horrendous weather in early June, where it rained heavily and consistently over several days. There was a brief break in the bad weather which only lasted a day, but then we had two days where it rained heavily and non-stop all day and night and well into the following day. It was also cold, with a strong wind blowing from the north. And nearly all our broods were around a week old when the bad weather hit, so they were all at a very vulnerable stage.

So when we were due to carry out the ringing later that same week, we were braced for some failures but it was worse than we feared. It was almost a complete wipeout… or washout might be a better description. Of 47 chicks due to be ringed that day, we had only 2 survivors. It was a grim day, with volunteers finding a mixture of dead chicks either in the nest or in the surrounding vegetation and territories ominously quiet with adults also absent. Some of us had seen it before and we all know it’s all part of the natural cycle, but it’s impossible to be indifferent when you experience something like that.

Judging by the age of the chicks when they died and counting back, we worked out that it was the weather on those final two days of the bad weather spell that did the damage… the cold and the wet and the struggle to find food finally too much for the chicks and adults.

SC chicks 9 days old Pylon 2019(1)In some good news, we had 6 chicks still alive in one of the nests that was slightly later than the others in timing. We worked out later that those chicks must have been hatching during those two days of the worst weather, so the female must have somehow sat it out.

It may have been helped by the aspect of her nest. Quite by chance she had built a nest in thick dead bracken with an almost impenetrable screen of it to the northern side of the nest and most of the bad weather was hammering in from the north. So hopefully, she was helped by the nest vegetation protecting both her and the chicks from the worst of the weather. When we checked the nest that day to see if they were still alive, we found both the nest and chicks warm and dry.

Piezos SC nest site 2019 cropShe seems to be a remarkable female Stonechat all round though as one of our volunteers on a Nightjar survey a few nights later saw her still catching moths by the light of the moon at nearly midnight. When we came to ring those chicks a week later, it was great to see such healthy thriving chicks – all 6 of them, and they’ve since fledged successfully.

The volunteers spent the week after the bad weather working out if the adult Stonechats were still alive and it looks like we may have lost another female as there’s been no sign of her since, although the male is still on territory and singing intermittently. Since then, another female also seems to have left her territory. She was still present the week after the rain but has not been seen recently and the male there now seems to be alone.

Both of these territories had first brood failures as well, one on eggs and the other on chicks, so two failures may well have prompted the females to end their breeding season. Even in a good seasons without failures, not all pairs go on to make 3 breeding attempts anyway.

Little Nose SC 2nd brood nest 2019The range of nests that failed were in a mixture of vegetation, from high up in thick heather to low down on the ground in grass tussocks, or in dead bracken which was both on dry banks or out on the wet mire. As is the pattern, 5 of the nests were close to paths in a mix of vegetation and at varying heights, both at ground level and in two cases, at head height in dead bracken with new growth above it.

There were several nests that faced north so were completely open to the weather. Some nests also had a relatively open aspect directly above them so the rain would effectively have drained down the vegetation straight into the nests, the angle of the approach to the nests almost acting like a funnel for the water, so some nests were thoroughly saturated. They really didn’t stand a chance in such conditions and the weather was just bad timing all round. A week or so later and more chicks might well have survived.

So out of a possible 52 chicks from this round of second broods on Dersingham Bog NNR, we ended up with only 8 fledged young – a very disappointing result given what might have been. We suspect our Tree Pipits’ first broods suffered similarly from the bad weather arriving at the wrong time, with most of the males now singing again and with only one pair seen food carrying. Our Nightjars seem to have weathered the storm, literally, and we are now up to 16 nests found, with a mixture of first and second broods (we’ll report on our so far terrific Nightjar season at a later date).

In the meantime, we look forward to our 3rd broods of Stonechats and some of our pairs are already on eggs, with our volunteers working hard to find the remaining nests from our 6 active pairs. So fingers crossed, we can make the most of the rest of the season.

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