Birds in Lincolnshire
How many pairs of Hobby breed in Lincolnshire?
How many pairs of Hobby breed in Lincolnshire? By Graham Catley
During 2000 I purchased a copy of the superb monograph on the Hobby by Anthony Chapman and published by Arlequin press. For a number of years in the late 1980's I was fortunate to be able to study several Hobby nests in the north of Lincolnshire but by the mid 1990's other species took precedence and I lost touch with breeding pairs at regular locations. Reading "The Hobby" gave me the spur to look again for this most beautiful and enigmatic species the status of which in Lincolnshire has always been somewhat clouded in mystery.
Although a regular breeding species in the county to the 1880's there was a steep decline at the hands of gamekeepers and possibly egg collectors leaving just a few pairs in the early twentieth century. There were then no proven instances of breeding until 1973. Since the late 1970's the number of reports of the species have increased dramatically and presumably so have the number of breeding pairs but where is the evidence? When I first watched a Lincolnshire Hobby nest in 1988 there were six pairs reported as proven nesting in the county. The maximum number ever reported seems to have been the 17 pairs recorded in 1994 since when the number recorded in each year has fallen with the species appearing to be again in decline. For a number of reasons I do not think that this is the case. In fact later I will come up with a figure for breeding pairs in Lincolnshire, based on logical distribution and twelve years of observations, that I am sure will make most people say "he's off his trolley".
Speaking to birders in north Lincs I have received a general impression that people are seeing less Hobbies now than five years ago and they are assuming that the species is declining. However, have people's birding habits changed? Do they spend less time on their local areas? Where do we spend most time watching birds? Water bodies crop up again and again; pits, reservoirs and of course the coast and all of these sites do attract feeding birds but Hobbies will travel up to 6km away from the nest to feed. So the chances of locating breeding birds from birding at water areas may be rather low unless of course a pair happen to nest close to such a site. None of the nests I have watched have been within visible distance of a known well watched birding site and most have in fact been in uninspiring farmland where birders would seldom if ever set foot. So to return to the first point of this paragraph does a decrease in the number of sightings mean that the species is now less common than it was in the early to mid 1990's? I am not in a position to state categorically either way but I would just quote two instances of Hobbies nesting close to areas where a lot of birding takes place and yet the number of annual sightings is remarkably low. In this context conversations with birders on the subject of breeding pairs repeatedly reveal the impression that "Hobbies cannot possibly be nesting near here as we do not see them regularly or even on a semi-regular basis". Of the two nests that I found in 2000 the first was within three miles of a series of Nature Reserves that are visited by many thousands of people throughout the summer. Good birders frequent the sites throughout the summer and yet there were only twelve sightings of Hobbies between April 24th and September. The second nest, that I had suspected but not found in previous years, was within two miles of areas where I spent in excess of 300 hours in the summer of 2000 and yet I had not seen a Hobby there until July when through a slice of luck I found the nest. Even following fledging when there were five Hobbies in the area I only recorded one bird away from the immediate area of the nest site in spite of many hours spent watching for raptors in the close vicinity. Kid yourselves not this is a very elusive species and the key to finding nesting pairs appears to me to be dogged persistence and a large slice of luck. As with studies of most raptors that occur at relatively low densities there is no substitute for large number of hours in the field and for lots of watching and waiting. Modern quick fire birding with its movement between different hot spot locations and a preference for listing per se does not fit in with the discovery of widely spread scarce breeding species. This is not a criticism of modern birding but an explanation of one of the reasons why I believe we have such a poor idea of how many Hobbies we have.
Chapman quotes a variety of breeding densities for comparable areas of eastern England. The most useful of these refer to areas where intensive studies have located the true density of breeding Hobbies. Densities that I have taken and used in my analysis as being of particular relevance to Lincolnshire range from the 3-4 pairs/100kmē in the south Midlands found by Fuller et al 1985, and the 4.1 pairs/100kmē found in a 840kmē study area in Southern Derbyshire to a probably more comparable density of 1.3 pairs/100kmē in the arable districts of south Cambridgeshire.
Looking at 12 100kmē that I know well in the north of the county Hobbies show a mean density equivalent to the 1.3pairs/100kmē given for Cambridgeshire with 15 pairs present. This may however, be a considerable underestimate of the true density over this area as some of the 10km squares include large areas of open heathland where the species could be spaced closer together but where they are in general more difficult to find than in open farmland. Extrapolating this density to the whole of Lincolnshire where there are about 70 100kmē would produce a total county population of 91 pairs. This of course takes no real account of variations in habitat but I would not suggest that the Fenland area is less suitable than most of the rest of the county and overall the habitat within Lincolnshire seems to be quite adequate for breeding Hobbies. The true population may be even higher than 100 pairs? And there go the off-the-trolley comments again.
P Prince and R Clarke (British Wildlife 4) suggested that the northward spread of the species in the UK may be closely tied in with the northward expansion of several species of dragonfly but notably Migrant Hawkers and Common and Ruddy Darters. With global warming bringing warmer summers and more dragonflies there may well be expectation of further increases in out Hobby population. It seems unlikely however, that the true status of the species will be revealed without an in-depth study by a dedicated team of Hobby lovers.
I would obviously be interested in other people's impressions of the current status of the Hobby in the county, especially in the south and south-west, where it should be at its most common? and also in any comments on this discussion paper.
Graham Catley May 2001
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