There are several things at play with the Avocets this year Peter. Whether as a result of habitat changes, lower water levels or even the increase in their numbers as well as an increase in BHG's I'm not sure but things are different.
First of all there is an increase in breeding Avocets up from 17 breeding pairs in 2016 to at least 22 pairs this year.
Over the last 35 years I have been thoroughly monitoring all aspects of the breeding cycle of all the waders at the Flashes. Our avocets are probably the most studied in the Country - thanks to Mike, Des, Dave J and Phil. We have details on nest site, incubation period, chicks hatched , survival rate and feeding zones and even behavioural patterns, etc etc. I digress .
Nest Sites:
This year many nests have been in the meadow in fact 10 nests in all. This is probably as a result of pressure by BHG saturating previously prime Avocet nesting islands. But also it is accommodating the new influx of breeding birds. Many of these were probably the non-breeders from last year.
Another well used area is in front of the hide. Here at least 8 nesting attempts were made. These mainland sites are as a result of the Fox fencing doing its job. In the early years only islands were used for nesting. But BHG have albut taken the islands and only 5 nests were on islands this year but not very successfully.
Feeding Zones: There are 10 feeding Zones most in front and either side of the hide. But only 2 along the meadow shore , where the highest mortality has been this year. Due to predators, too much pressure from neighbouring avocets or too small a feeding area to sustain growth of chicks I am not sure. But very few proportionately of the chicks are surviving. It could also be due to low water levels being too muddy with little amounts of food.
Another frequently used area in the past was along the eastern shore of 2nd Flash. But this has been totally ignored this year and I would suggest that the stock fencing is the only reason for this.
Brood size:
Although we have many more pairs these days this does not mean we get more chicks. This year's brood sizes have been on average the lowest ever. This could be due to parents abandoning incubation of the whole clutch rather than fewer eggs being laid. I have noticed on several occasions sitting birds leaving un-hatched eggs to help the other parent defend the 1st hatched chick. The threats could be from LBBG, buzzards or even neighbouring avocets attacking the chicks. While unatended eggs have been stolen by coots and moorhens. The pressure on the new chicks sometimes forces the parents to cut their losses and take what they've got resulting in small broods.
I hope this answers some of your questions Peter and next time I see you I will elaborate 8-P