Grey Heron - 2003-07

Grey herons generally nest in mature trees, deciduous tree species such as oak and beech together with conifers such as Scots pine. Cliff-nesting Grey Herons have been recorded on parts of the St. Brides Bay coast in the 1960’s and 70’s, there have even been instances of ground-nesting (Donovan & Rees, 1994).

Between the 1984-88 and 2003-07 surveys, there have been changes in the distribution and numbers of heronries in the county. The number of tetrads where breeding was confirmed dropped from 10 to 8.  The data obtained from the BTO heronries census show that between the two surveys, at least one established heronry was lost, Shipping Wood, which was clear-felled in the late 1990s, and the oldest continuously occupied heronry in the county at Slebech fell into disuse in 1995/96 when the birds relocted to another site on the Western Cleddau. 

The heronries census also includes records of single nests in several parts of the county, though these tend to be occupied only sporadically.  Such sites were recorded at Templeton, Westfield Pill, Bosherston Lily Ponds and Crygmarren Pool during the 2003-07 survey.

It can be difficult to locate nest sites and to confirm the breeding status of Grey Herons, especially once the leaves have come out on deciduous trees, or in dense conifer plantations where access can be difficult.  This could explain the relatively high number of possible breeding records (not included on the maps), especially if these involved pairs nesting singly away from the established colonies.  Total numbers of breeding pairs vary from year to year, and it is difficult to accurately estimate the size of the breeding population. 

In 2007, the five heronries that were counted as part of the heronries census yielded a total of 35 pairs.  In the mid-1990s the number of pairs regularly exceeded 40 and peaked at 60 in 1997. The total breeding population could therefore be somewhere between 40 and 70 pairs. Donovan & Rees (1994) quote a range of between 30 pairs when the population is at a low ebb, e.g. following the harsh winter of 1962-63 and 65 pairs in more favourable times.

Jane Hodges

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 8 (1.6%)

Orange = breeding probable = 3 (excluded from total)

Total tetrads in which registered = 11