2022
Schommelingen in de broedvogelstand van Exloo, een esdorp aan de rand van het Drents plateau, tussen 1976 en 2022
Publication
Publication
Fluctuations in the breeding bird fauna of Exloo, a small village in East Drenthe, in 1976-2022
The village of Exloo, with 1680 inhabitants in the 2020s, is one of several hundreds of such villages in the rural province of Drenthe in the northern Netherlands. It grew in size from 46 ha in 1945 to 88 ha in 2007, and is surrounded by (mostly arable) farmland except forest and heathland in the west. The density of the built-up area within the village has increased over time, as has the number of larger buildings. This has led to the loss of small open spaces in between houses. The village streets are lined with deciduous trees (mostly Quercus robur) and many gardens have lawns and shrubs. Garden design has been subject to change, with popularity of lawns, conifers, shrubs, concrete tiles and pebbles coming and going. The number of nestboxes is unknown, as is the evolution of nestbox numbers over time (apart from a loss in the public zone). Also, the number of free-roaming cats is unknown, apart from being substantial. From 1996 onwards, hundreds of ha of farmland near the village have been converted into marshland or covered with solar panels (the latter starting in the 2020s). Breeding birds have been censused by the same observer since 1976 (when 24 years old). Census methods were the same over the years, with five complete rounds from March through June, each round taking four days to complete (with early mornings specifically targeted at species active at dawn). As an inhabitant of Exloo, the census taker was able to incorporate chance observations whenever possible. To counter hearing loss, around 2013 a hearing aid was added to the standard equipment. Over the 47 years of study, a total of 77 bird species were registered as a breeding bird, of which 16 species never exceeded one pair in any one year. Eight species were recorded at least once with >100 pairs, ranging from Blue Tit (102 pairs in 2010) to House Sparrow (210 in 2020). Thirteen species disappeared as a breeding bird, usually uncommon species but including Turtle Dove (still 6 pairs in 1983), Mistle Thrush (maximum 8 pairs in 1991), Icterine Warbler (maximum 10 pairs in 1986) and Rook (up to 195 nests in 1984). Newcomers hardly ever attained >3 pairs (e.g. White Stork 1, Barn Owls up to 3, Tawny Owl 1, Goldfinch up to 3) except Jay (up to 9 pairs) and Hawfinch (up to 7 pairs). The overall trend in 1976-2022 was a steady, threefold increase in numbers and biomass from the late 1970s (when 91 pairs/10 ha) till the mid-1990s (176-183 pairs/10 ha), during which the impact of severe and cold winters (1978/79, 1984/85-1986/87) was short-lived or negligible, as was the Great Drought in the Sahel, which reached its nadir in the mid-1980s. Breeding bird numbers declined after the 1990s to 127-139 pairs/10 ha in 2015-22. During the entire study period of 1976-2022, the number of houses increased by 20% (with a concomitant decline of open spaces in the village itself), but the number of breeding birds by 40-52%. It is unknown whether the discrepancy can be explained by ‘greening’ of the village (gardens, for example). On the species level trends were widely different, from increases to steep declines of >50% and (near-)disappearance (e.g. Streptopelia decaocto, Turdus viscivorus, Prunella modularis, Phylloscopus trochilus, Sylvia borin, Spotted Flycatcher, Certhia brachydactyla, Sturnus vulgaris, Corvus frugilegus (persecuted to extinction), Coloeus monedula, Passer montanus) to consistent declines since the late 1990s (Columba palumbus, Motacilla alba, Phoenicurus ochruros, Troglodytes troglodytes, Turdus merula (starting 2007, i.e. before the advent of Usuta virus), T. philomelos, Pica pica (since mid-1980s in decline), Fringilla coelebs and Carduelis chloris (after 2010). Far fewer species showed a consistent increase, often stabilizing to some extent in the 2000s, such as Hirundo rustica (profiting from newly built stables for ponies, horses and sheep, perhaps also from the creation of wetlands nearby), Erithacus rubecula, Sylvia atricapilla, Parus major, Cyanistes caeruleus (but decline in recent years), Nuthatch (colonized the village in the 1990s) and Passer domesticus. Despite the bewildering variety in trends, some overriding factors may be discerned. Many species that depend on nearby farmland for food have shown steep declines, no surprise given the intensification of farmland and the concomitant decline of insects, earthworms and cranefly larvae. Species breeding and feeding in gardens showed mixed fortunes, but mostly negative trends in recent decades. Despite the increase in number of inhabitants (and houses + gardens, i.e. theoretically an increase in nesting and feeding opportunities), an ecological trap may have been created with high cat-related mortality, a high incidence of diseases created via bird concentrations at bird tables, and the preference for ‘clean’ gardens. The loss of messy gardens and ditto farmland is likely to have converted attractive bird habitat into wasteland (not to mention the creation of large solar parks on nearby farmland, starting in the 2020s), a trend exacerbated by a parallel loss of invertebrate food. The fact that many resident birds and short-distance migrants show consistent declines since the 1990s, whereas some long-distance migrants partly bounced back as soon as rainfall in the Sudano-Sahel improved after the 2000s, indicates that local conditions as well as those in Africa play a role in the fortunes of birds breeding in a small village in a small country in a tiny part of the Palearctic
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Drentse vogels | |
CC BY 3.0 NL ("Naamsvermelding") | |
Organisation | Werkgroep Avifauna Drenthe |
J. Santing, & R.G. Bijlsma. (2022). Schommelingen in de broedvogelstand van Exloo, een esdorp aan de rand van het Drents plateau, tussen 1976 en 2022. Drentse vogels. |