ISSN:
1439-0361
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Description / Table of Contents:
Summary In an area near Cologne habitat separation of three raptor species was investigated (for area description seeKostrzewa 1985 a and for raptor communityKostrzewa et al. 1985). According to earlier research data for ‘horizontal-habitat-selection’ (HHS), ‘vertical-habitat-selection’ (VHS), intra- and interspecific competition (as ‘nearest-neighbour-distance’) have been collected for 113 ha circular plots (600 m in diameter around the nesting place). 33 different variables characterize each plot (Tab. 1). The following number of different plots have been performed: 52 for Common Buzzard, 28 for Honey Buzzard and 25 for Goshawk. The data are evaluated by means of multivariate statistic: principal component analysis (PCA) and stepwise discriminant analysis (DA). Due to the very good indications of niche separation between these species in question there was no need of investigating ‘feeding-selection’ (FS). No significant separation could be found in VHS parameters (Abb. 1). Habitat separation is evident in HHS but without marked difference between the species. Niche overlap is significant indicating competition. The results of the different analyses are in accordance with the competitive-exclusion-principle. For all species pooled data have been evaluated with PCA. Habitat choice basically depends on the components: a) an ecological environment, b) on human interference and c) on interspecific competition (Tab. 3). The results of different DA's show the following: A set of variables which characterizes the natural environment of the raptor has been tested (Abb. 2). It could be pointed out that this method actually reflects the general reasons of habitat choice: Common Buzzard prefers plots of mixed forest covered or open land and breeding places close to the edge of a wood. Goshawks prefer breeding places in larger distance to wood edges, also open land with a tendency for forests. Honey Buzzards show no special preference, but they choose often more wide woodland areas. By means of the whole set of variables for each species we got results more close to those of the PCA: variables such as human interference (roads, built up areas and so on) and interspecific competition lead to variations in habitat choice and result in habitat separation: Goshawks are only found in uninfluenced plots where there is ± no human interference. Honey Buzzards rather tolerate disturbances. The behaviour of the Common Buzzard is found between these extreme demands (Abb. 3). The same set of data has been used to compare habitat choice between the species:Accipiter andPernis are widely separated, mostly due to human interference and interspecific competition, but also to variables concerning the landscape: distance to forest boundaries and size of used wood lots (Tab. 6, Abb. 4).Accipiter andButeo: distance to forest edges, lanes and to the nearest neighbour define the separation of these species.Pernis andButeo are found to be less separated. The dessicive factors are size of forest area, distance to forest edge, length of edges to clearings, distance to nextAccipiter and number of raptor neighbours within a distance of 2000 m.
Notes:
Zusammenfassung In der Niederrheinischen Bucht wurde eine quantitative Analyse von Greifvogelhabitaten anB. buteo, A. gentilis undP. apivorus durchgeführt. In Anlehnung an andere Untersuchungen wurde eine Methode entwickelt, die die Wahl der Horizontalen-Habitat-Selektion (Wahl des Landschaftsausschnitts in Form eines kreisförmigen 113 ha Plots) die Vertikale-Habitat-Selektion (Vegetationshöhe) und die intra- und interspezifische Konkurrenz (als Nearest-Neighbour-Distance) mit insgesamt 33 Variablen (Tab. 1) berücksichtigt. Die Auswertung erfolgte mittels multivariater Statistik: Hauptkomponentenanalyse und schrittweiser Diskriminanzanalyse. Andere Untersuchungen belegen, daß die Nischentrennung bezüglich der Nahrungswahl sehr groß ist. Bei der Wahl der Vegetationshöhe konnte keine signifikante Trennung festgestellt werden. Die Trennung der Arten ergibt sich bei der Wahl des Landschaftsausschnitts durch Unterschiede bei verschiedenen Variablen. Überschneidungen, d. h. die Ähnlichkeit der Habitate, sind teilweise jedoch so groß, daß Wechsel von Brutplätzen zwischen den Arten vorkommen können. Bei der Habitatbesetzung stellt die interspezifische Konkurrenz eine meßbare Beeinflussung dar, sie entspricht den Nischenüberlappungen zwischen den Arten. Die vorliegenden Ergebnisse stehen im Einklang mit dem Konkurrenz-Ausschluß-Prinzip.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01661696
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