Columba livia var., Feral pigeons, Urban birds, Jena city, Germany
Reception date: 11/01/2010 | Acceptation date: 27/05/2010 | Publication date: 30/06/2010
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A study of feral pigeon Columba livia var. in urban and suburban areas in the city of Jena, Germany
A study of feral pigeon Columba livia var. in urban and suburban areas in the city of Jena, Germany
A population of feral pigeons, Columba livia var. was conducted in the city of Jena, Germany, from July to December 2007. Daily censuses were conducted by walking ten transects in a selected area of the city, five transects in built up areas and five in the suburbs. Pigeon population density was higher in urban areas than in suburbs but differences were not significant. Main behavioural activities recorded were resting, preening, flying, eating, sunning and roosting. Regular locations of activities were rooftops and roof edges in urban areas, and rooftops, eaves on balconies in suburban areas. The plumage phenotype most frequently recorded in both areas was Blue bar.
Key words: Columba livia var., Feral pigeons, Urban birds, Jena city, Germany
Estudio de la paloma doméstica Columba livia var. en áreas urbanas y suburbanas en la ciudad de Jena, Alemania
Se estudió una población de palomas domésticas, Columba livia var. en la ciudad de Jena, Alemania, entre julio y diciembre de 2007, a través de censos diarios en diez transectos de un sector de la ciudad, cinco en áreas urbanas y cinco en suburbanas. La densidad poblacional de palomas en zonas urbanas resultó ser mayor que en zonas suburbanas, sin embargo no se encontraron diferencias significativas entre ambas áreas. Las actividades de comportamiento registradas por las palomas fueron de descanso, de mantenimiento del plumaje, de vuelo, alimentación, baños de sol y asentadas en perchas. Las actividades se producen el lugares como techos altos y aleros en edificios en zonas urbanas y parte superior y bajo techos de viviendas en zonas suburbanas. El fenotipo de plumaje más abundante para ambas áreas durante el periodo del censo fue Blue bar.
Palabras clave: Columba livia var., Paloma doméstica, Aves urbanas, Jena, Alemania
Estudi del colom domèstic Columba livia var. en àrees urbanes i suburbanes de la ciutat de Jena, Alemanya
Es va estudiar una població de coloms domèstics, Columba livia var. a la ciutat de Jena, Alemanya, entre juliol i desembre de 2007, mitjançant censos diaris en deu transsectes d’un sector de la ciutat, cinc en àrees urbanes i cinc en àrees suburbanes. La densitat poblacional de coloms en zones urbanes va resultar més gran que en zones suburbanes, però no es van trobar diferències significatives entre les dues àrees. Les activitats de comportament registrades pels coloms van ser de descans, manteniment del plomatge, vol, alimentació, banys de sol i estades en perxes. Les activitats es produeixen en llocs com ara sostres alts i ràfecs d’edificis de zones urbanes i la part superior i sota teulada d’habitatges de zones suburbanes. El fenotip de plomatge més abundant a les dues àrees durant el període del cens va ser Blue bar.
Paraules clau: Columba livia var., Colom domèstic, Ocells urbans, Jena, Alemanya
Pigeons were originally found wild in Mediterranean bordering countries, on coasts and cliffs of Europe, North Africa, and Western Asia. They were later introduced and colonized in North, Central and South America and all over Europe (Baptista et al., 1997) in both tropical and temperate regions (Gompertz, 1957; Goodwin, 1954, 1960). They are now distributed worldwide and live mainly in urban environments (Haag-Wackernagel, 1998, 2003) where they cause health problems for humans and domestic animals, carrying virus, bacteria, fungi, protozoa and parasites (Cena et al., 1989; Cerri et al., 1989; Baldaccini, 1991; Straff et al., 2001; Trovnicek et al., 2002; Haag-Wackernagel & Spiewak, 2004), and damage buildings and monuments (Johnston & Janiga, 1995; Haag-Wackernagel, 1998).
The species has a large range, with an estimated global occurrence of ten million km². The European breeding population has been estimated at 17-28 million individuals (BirdLife International, 2004). Several studies have estimated city populations, with results showing, for example, 103,650 birds averaging 570 ind/km2 in Milan (Sacchi et al., 2002), and 14, 200 individuals averaging 44 birds 10-1 ha in Gdansk, Poland (Hetmanski & Jarosiewicz, 2008). A census for Barcelona city in 1990 reached 183,887 ± 14,914 and a density of 2,849 ± 231 ind/km2 (Sol & Senar, 1995) but more recent research estimated 270,743 ± 36,815 (Senar et al., 2009).
This present work is the first study of Columba livia var. in the city of Jena, Germany, and it reports on a daily census of behavioral activities, plumage phenotypes and breeding data at urban and suburban areas.
Material and methods
The study was carried out from July to December 2007 in Jena city, Germany (fig. 1) (50º 55′ N, 11º 34′ S). In an attempt to estimate the Columba livia population in the city, we chose a delimited area, including the built up centre and suburban areas. Five suburban east-west transects were defined and measured as followed: 1.28 km, 1.32 km, 0.46 km, 0.40 km, 0.39 km, with 0.25-0.35 km approximately between transects, occupying a total of 3.85 km2 suburban area. Another five urban north-south transects were also measured: 1.02 km, 0.70 km, 0.80 km, 0.37 km, 0.40 km occupying a total area of 3.29 km2.
Censuses were conducted using binoculars and digital camera four to five days per week. We recorded both stationary and moving birds in the transect dimension, two hours before and after midday following Uribe et al. (1984), Senar & Sol (1991), Montalti & Kopij (2001). Pigeon density (individuals per km2) was calculated from the census transects per area. Urban areas were characterized by high buildings, churches, cafés and food shops, buses and cars. Such buildings resemble rocky sea cliffs, an ideal synantropic environment for feral pigeon settlement. Suburban areas consisted of residential houses, few shops and little traffic.
Behavioural activities were recorded using binocular observation on daily census while walking on street transects. We registered resting, preening, sunning, eating, flying, nesting, roosting, drinking, sleeping, perching, and mating.
Plumage phenotypes were recorded using binoculars, camera and bird guides on daily census from July to December. These data were later classified per month and per area (Goodwin, 1970; Murton et al., 1973, 1974; Johnston & Janiga, 1995; Miller, 1997).
Breeding activity was measured monthly (seven visits) at the tower of Lobeda locality (50º 52′ N, 11º 35′ E), 7 km from Jena. The tower contained twenty experimental wooded nest boxes occupied by pigeons where we classified bird stages. At Jena, breeding was measured on transects by registering nesting on walking census in both areas.
Feral pigeons density during census was higher in urban transects, 730 ind/km2 ± 199 with a total number of individuals of 2,377 (61%), than in suburban transects, 392 ind/km2 ± 205, with a total number of 1,510 (39%) pigeons (fig. 2). However, differences between the two areas were not statistically significant (a = 0.05; F = 1.52; p > 0.24). A t-test, considering different variances analysis, showed no significant differences (p > 122; t > 1.23). Mean values of pigeons per transect were 396 in urban areas and 251 in suburban areas.
Columba livia behavioural activities were registered on transects in both areas. Comparison of pigeon activities showed no significant differences between urban and suburban areas in any month except December (a = 0.05; F = 7. 33) (taula 1, fig. 3).
Plumage phenotypes were Blue bar (Bb, N = 542 ± 44), B Checker (Bche, N = 169 ± 20), T Checker (Tche, N = 91 ± 8 ) Blue Dark (Bdark, N = 29 ± 6) Brown bar (BBrown, N = 31 ± 5) and B Light (Blight, N = 16 ± 2) (fig. 4). Comparison of months to detect differences in coloration patterns revealed no significant differences using ANOVA analysis. The most abundant plumage phenotype was B bar: 56% in July, 71% in August, 60% in September, October and November, and 56% in December.
Breeding activities in both localities and areas were performed by checking presence of birds, nesting and mating (taula 1) and registering number of adults N = 12 ± 2, fledglings N = 10 ± 1, small chicks N = 6 ± 1, eggs N = 13 ± 1, and number of active N = 25 ± 2 and non-active nests N = 13 ± 2. Variance analysis showed no significant differences between these bird stages at the tower (fig. 5).
Feral pigeon urban density was higher than suburban density but differences were not statistically significant. Urban areas were characterized by high buildings that were architectonically favourable for pigeon settlement: old, grey, abandoned, rocky-walled churches and some empty domes were favoured. In suburban areas they favoured greenish landscape, low houses. Differences in population density were expected between areas but lack of significant findings may be due to the boundaries chosen Jena may not correspond structurally to a classical European gothic city. The city was largely rebuilt after World War II, leaving a mix of old centre patches in the middle of suburban neighbourhoods. To find differences between areas it could be interesting to conduct a study comparing the outer city with a suburban area.
Blue bar (62%) was the most abundant plumage followed by Checker (19%) and T Checker (10%). The study of a probable phenotype-dependant selection in an urban environment such as Vienna showed that natural distribution was 30% of Blue bar and 28% of Blue Checker. Bird activities were similar in both areas without significant changes.
L. M. J. wishes to thank the supervisor at the Polar & Bird Ecology Group in Jena for educational and logistical material and for constant support during her DAAD grant stay. Thanks also to DAAD and the Spanish Ministry of Education, Science and Technology for fellowship support, and CONICET.