Passer Domesticus) in the Faroe Islands
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237 A history of colonization and current status of the house sparrow (Passer domesticus) in the Faroe Islands Ein søgulig lýsing av búsetingini hjá gráspurvanum í Føroyum og støðu hansara í dag Sven-Axel Bengtson 1, Kirstin Eliasen2, Laura Mary Jacobsen2 and Eyðfinn Magnussen2 1. Museum of Zoology, University of Lund, Helgonav.3, SE-223 62, Sweden. Email: [email protected] 2. Fróðskaparsetur Føroya, FO-100 Tórshavn, Faroe Islands. Emails: [email protected], [email protected], [email protected] Úrtak Abstract Gráspurvur (Passer domesticus) eigur í flestu býum The house sparrow (Passer domesticus) breeds commonly og bygdum í Føroyum. Rættilig niðurseting byrjaði in built-up areas throughout the Faroe Islands. The miðskeiðis í 1930unum, og síðani hevur hann spreitt colonization began in the mid-1930s and the subsequent seg um oyggjarnar. Úrslitini í greinini eru grundaði spread is described on the basis of previously published á nýggjar teljingar, samrøður við fólk og skrivligar records, interviews with local people, and recent surveys frásagnir. Spjaðingarmynstrið er torskilt, bæði tá hugt of all habitations. Spatio-temporal pattern of spread is verður at búsetingarmynstrinum kring landið, og hvussu complex lending support to previous suggestions of hetta broytist við tíðini. Kanning okkara vísir, at tað possible, independent immigrations. It is suggested helst eru fleiri sjálvstøðugir tilflytarar, og stuðlar hetta that the process of spread was influenced by the undanfarnar metingar. Alt bendir á, at spjaðingin av agency of man, geographical isolation (water-barriers gráspurvi er tengd at fólki, og í hvønn mun bygdirnar and topography), and local conditions and population eru avbyrgdar. Eisini hava livilíkindi og broytingar av dynamics. Until now 80 % of the settlements (n = 118) stovninum á staðnum nógv at siga. Kanningin er gjørd have been more or less permanently colonized: first the í 118 bygdum og býum, og vísir hon, at gráspurvur larger ones (nearly all before 1960) and within 30-40 búleikast í 80 % av teimum. Gráspurvurin tók fyrst búgv years c. 50% of those currently colonized (65% in the á teimum størru plássunum í landinum, og var at finna early 1980s). Total breeding population in 2001 and 2002 á flestu teirra fyri 1960. Tey fyrstu 30-40 árini búsettist was estimated at c. 2,500 and 2,700 pairs, respectively; gráspurvurin í 50% av føroysku bygdunum, og í fyrru one-third being recorded in the capital Tórshavn (90 helvt av 1980unum hevði hann breitt seg til 65% av pairs/km2). The numbers (total and local) have fluctuated bygdunum. Stovnsstøddin í 2001 og 2002 var mett at (though precise historical data are scarce) but currently vera ávikavist 2.500 og 2.700 pør. harav ein triðingur no trend is discernible. er í Tórshavn (90 pør/km2). Talið av gráspurvi hevur verið eitt sindur óstøðugt, bæði í hvørjari bygd sær og samlað fyri landið. Lítið er til av søguligum tilfari um stovnsstøddina gjøgnum árini, og í løtuni hómast eingin týðilig broyting í gráspuvameinginum. Fróðskaparrit 51. bók 2004: 237-251 238 A HISTORY OF COLONIZATION AND CURRENT STATUS OF THE HOUSE SPARROW (PASSER DOMESTICUS) IN THE FAROE ISLANDS Introduction history of the house sparrow’s colonization The house sparrow (Passer domesticus) of the Faroes. is a companion of man, and aided by in- troductions and other human activities, it has successfully colonized many regions Material and methods worldwide (Long, 1981; Summers-Smith, Human habitations, in the following referred 1988). Before the start of its colonization to as settlements, are to be found on all 18 of the Faroe Islands in the late 1930s, the islands except for Lítla Dímun and range in house sparrow was considered a very rare size from a single farmstead or small village vagrant, in fact having been recorded only to the capital Tórshavn (15,000 inhabitants once (Andersen, 1901; Salomonsen, 1935; in an area of 8.72 km2). Mostly they form Williamson, 1945). Today it occurs abun- discrete units (the Faroese bøur, or infields) dantly all over the Faroes and is confined but in a few places settlements merge as to and breeds, or has bred, in virtually all e.g. along Skálafjørður (Eysturoy), around built-up areas. In the British Isles, Scandi- Tvøroyri (Suðuroy), and around Tórshavn navia, and elsewhere in Western Europe, the (Streymoy). All but two (Vatnsoyrar and house sparrow has decreased in numbers Kambsdalur) of the settlements are situated since the 1970s (markedly in the 1980s), by the sea. especially in urban areas (Hansen, 1985; The field-work was carried out intermit- Summers-Smith, 1999; Hogstad and Øien, tently between early April and mid-June 2001; Lindell, 2002). As to the Faroes, the and included 101 settlements in 2001 (all population has undoubtedly fluctuated and, censused by SAB) and 118 in 2002 (mostly at least for a period of time, probably de- censused by KE and LMJ). In a few in- clined in numbers; though in the absence stances, we had to rely on information from of systematic counts the evidence is mostly local people, mostly stating that there were circumstantial. no house sparrows to be seen in the respec- In this paper we report on studies of tive settlements. The census work usually house sparrows carried out in 2001 and started at dawn and continued until early 2002 when each year effectively all built- afternoon, with a break at mid-day when up areas (i.e. settlements) were censused the activity of the house sparrows was during the breeding season and the number markedly lower. The time spent in each of pairs estimated. During the course of settlement varied considerably depending the field-work, we also interviewed local on the circumstances (area, complexity of people about the history of the house spar- habitation, numbers of birds, and weather) row in the respective settlements. These from 15 minutes at a single farmstead to amendments to the previously published one hour in a small settlement and one data (see Jensen and Kampp, 1997) form day in the towns. Tórshavn was divided an improved basis for a comprehensive de- in 23 sub-areas that were surveyed over a scription and a tentative discussion of the number of days. On some occasions, the EIN SØGULIG LÝSING AV BÚSETINGINI HJÁ GRÁSPURVANUM Í FØROYUM 239 OG STØÐU HANSARA Í DAG censuses were interrupted due to unfavour- difficult to spot. Already before leaving a able weather conditions. We invariably fol- settlement, we made a preliminary estimate lowed the same procedure by starting at one of the number of pairs present taking into end (or opposite ends when more than one account the prevailing circumstances. We observer participated) and slowly walking have made no specific attempts to evaluate through the settlement. All parts of the set- the accuracy of our counts but in some in- tlements were visited and all house spar- stances we were able to make preliminary rows heard or seen were recorded. Special comparisons between observers and found attention was paid to gardens with lush a reasonably good agreement and hence vegetation, plantations, cemeteries, com- consistency. The counts and subsequent es- mons, older buildings, warehouses, farm- timates should therefore allow us to com- houses, sites where domestic fowl was kept pare settlements and years. Throughout and fed, and open utility patches of ground the study, we made a point of obtaining in- with more or less disturbed vegetation. Be- formation on birds and wildlife in general sides, in order to avoid counting the same and the house sparrow in particular (espe- birds more than once, we watched out for cially year of colonization and changes in sparrows flying in or out of sections of the number) by interviewing local, preferably settlement already visited. This was greatly elderly people in the field and through pub- facilitated by the smallness of many settle- lic media (newspapers, radio, and TV). For ments (often < 100 m across) and/or by the each settlement, we also noted the presence fact that the settlements are often located of grown-up gardens and plantations and along one main street running parallel to farming activities. Data on area was ob- the seashore. This, of course, did not apply tained from the MapInfo computer program to some of the largest settlements, which using topographical electronic map for the have a more complex structure. Thus, Tórs- Faroes (scale of 1:20,000). We also have havn had to be surveyed over a period of had access to unpublished data collected in time and possible effects of movements of 1981 (see Bengtson and Bloch, 1983). birds between the different subareas cannot be evaluated. History of colonization We recorded the sex of each bird (usually Fig. 1 shows in some instances the pre- not possible for flying birds) and whether cise, or more often the approximative, year it was observed alone, as one of a pair or of first colonization of house sparrow for in a flock. The house sparrow is a gregari- some 40 settlements for which information ous and semi-colonial species and even is available. in relatively small settlements, there was often more than one aggregation of birds. The southern islands Males were easily located as their calls Suðuroy (164.6 km2) was the first island to were readily heard also in drizzle and light be colonized by the house sparrow on the rain, while the silent females were more Faroes. This was in the winter of 1935-36 240 A HISTORY OF COLONIZATION AND CURRENT STATUS OF THE HOUSE SPARROW (PASSER DOMESTICUS) IN THE FAROE ISLANDS Fig. 1. First colonization of house sparrow at settlements in the Faroe Islands. Asterisks indicate previously published information referred to in the text. The arrows show the first colonization and two tentative subsequent colonizations.