Journal of Ornithology

, Volume 154, Issue 3, pp 655–662 | Cite as

Bird traits in urban–rural gradients: how many functional groups are there?

Original Article


Recent analyses of communities have examined the variation of species traits along environmental gradients. These papers highlight a combination of several traits, instead of variation of individual traits, to better explain the effect of urbanization on bird communities. Exploratory factor analysis (EFA) allows the identification of an underlying structure of a broad set of data. EFA can be a useful tool for generating functional groups from highly correlated biological traits in bird communities and determining its variation along gradients of urbanization. Birds were counted along an urban–rural gradient during spring 2009–summer 2010. Species were classified using 15 biological traits related to the use of space. The EFA was calculated from a matrix where rows were sampling units (n = 75), and columns represented counts of individuals with each trait (n = 15). Four functional groups were obtained. Functional group 1 comprised resident species feeding gregariously on the grond, nesting in buildings, having an omnivorous diet, and being most abundant in the more urbanized areas. Functional group 2 was most abundant at intermediate levels of urbanization and represented solitary species that nest in trees, feeding on vegetation and with carnivorous and nectarivorous diets. Migratory behavior, insectivorous and granivorous diets, aerial feeding and ground nesting were representative of two functional groups in rural areas. Responses to urbanization by these functional groups are consistent with the classifications of response guilds (urban exploiters, urban adapters, and urban avoiders). Thus, EFA allows a link between concepts generated from the analysis of species and the analysis based on biological traits.


Exploratory factor analysis Urbanization Guilds Birds Argentina Land use 


Merkmale von Vögeln entlang von städtisch-ländlichen Gradienten: Wie viele funktionelle Gruppen gibt es?

In aktuellen Untersuchungen von Vogelgemeinschaften wurde die Variation von Merkmalen an Arten entlang von Umweltgradienten untersucht. Diese Untersuchungen betonen eine Kombination verschiedener Merkmale, anstatt einer Variation individueller Merkmale, um den Effekt der Urbanisierung auf Vogelgemeinschaften besser zu erklären. Eine Erklärende Faktoranalyse (EFA) erlaubt es, in einem großen Datensatz eine zugrundeliegende Struktur aufzudecken. EFA kann ein nützliches Werkzeug sein, um aus hoch miteinander korrelierten biologischen Merkmalen in Vogelgemeinschaften funktionelle Gruppen zu erzeugen und um deren Variation entlang von Urbanisierungsgradienten zu bestimmen. Vögel wurden entlang eines städtisch-ländlichen Gradienten während des Frühlings 2009 bis Sommer 2010 gezählt. Die Arten wurden anhand von 15 biologischen Merkmalen zur Raumnutzung klassifiziert. Die EFA wurde aus einer Matrix berechnet, deren Reihen den Zählstellen entsprachen (n = 75), und in deren Spalten die Anzahl der Individuen mit dem jeweiligen Merkmal (n = 15) stand. Wir erhielten vier funktionale Gruppen. Die funktionale Gruppe 1 bestand aus Arten, die Schwärme bilden, in Gebäuden nisten, eine omnivore Ernährung aufweisen und am häufigsten in den am meisten urbanisierten Gegenden vorkommen. Die funktionale Gruppe 2 war am häufigsten in Gebieten mittlerer Urbanisierung zu finden und bestand aus Arten, die in Bäumen nisten, die sich von Pflanzen ernährten und solchen mit carnivorer und nectarivorer Ernährung. Zugverhalten, insektivore und granivore Ernährung, Nahrungsaufnahme im Flug und Bodenbrüten waren kennzeichnend für zwei funktionelle Gruppen in ländlichen Gegenden. Die Reaktionen dieser funktionalen Gruppen auf Urbanisierung stimmen überein mit den sog. Reaktions-Gilden (Stadtnutzer, Stadtanpasser und Stadtvermeider). Daher erlaubt die EFA eine Verbindung zwischen Konzepten, die auf der Analyse der Art beruhen, mit Analysen, die auf biologischen Merkmalen fußen.



The idea of this manuscript appeared in the postgraduate course “Análisis Factorial Exploratorio” taught by Dr. Ledesma. I really appreciate the improvements in English usage made by F. Isla and Peter Lowther through the Association of Field Ornithologists’ program of editorial assistance. The suggestions made by J. Isacch and R. Ledesma and two anonymous reviewers improved the quality of the manuscript. I thank F. Isla for the production of Fig. 1. The author is a fellow of CONICET.

Supplementary material

10336_2012_928_MOESM1_ESM.doc (84 kb)
Supplementary material 1 (DOC 84 kb)


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2013

Authors and Affiliations

  1. 1.Universidad Nacional de Mar del PlataMar del PlataArgentina

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