Feeding ecology of the common wood pigeon (Columba palumbus) in a major European city

The study area is located within the municipality of Madrid, the capital and most populated city of Spain.

From October 2021 to September 2022, a survey of the feeding patterns of the common wood pigeon was conducted. To detect common wood pigeons eating both in the ground and trees, we walked transects in parks and streets (henceforth urban matrix) at least 5 times per season alternating morning/afternoon. In total, we walked 307 transects: 141 in parks and 166 in the urban matrix. In summer, late spring and early autumn, the census was conducted between the first 3 hours after the sunrise and the 3 last hours before sunset. During the coldest periods of the year, especially in winter when the days are shorter, the census was conducted from 10 AM -12 AM and 4 PM -6 PM. In parks and gardens, we covered the available pedestrian paths, avoiding passing through the same place on the same transect. In the urban matrix, we covered as many streets as possible in each transect, without passing through the same street twice, and avoiding those that had previously been discarded for lacking trees. We used binoculars to avoid misidentification with other birds and to be sure of the items consumed by the pigeons in each tree. We included only those observations in which the pigeons were seen feeding, being conservative in case we had doubts about what part of the tree they were eating. We excluded non-feeding events: drinking, sunbathing, resting, collecting nest material or moving among the branches without clearly perceiving any foraging behaviour. 

We considered the urban matrix streets, avenues, small parks (less than 5 hectares) and public and private gardens integrated in the study area. ‘Parks’ refer to the historical green areas located within the city: Parque de El Retiro (114,19 hectares), Parque del Oeste (79 ha), Parque de la Dehesa de la Villa (64,17 ha), Real Jardín Botánico de Madrid (7,8 ha) and Quinta Fuente del Berro (7,42 ha); and other large green areas such as Campo del Moro and Parque de Atenas (which together form a continuum of 27,4 ha) and 6.5 kms of the urban section of the Manzanares river together with its adjacent parks, especially Parque Madrid Río (approx. 35 ha). Moreover, we classified the observations as ‘ground’, when the pigeons were observed feeding grass, elm samaras and other seeds or small stones on the ground, and ‘trees’ when we observed them feeding on branches of trees. When more than one individual common wood pigeon per tree was observed, we registered the abundance. We classified the trees as native or exotic according to Flora Ibérica. In case of uncertainty in the identification of the tree species, we consulted the inventory of trees published for each park (Directorate for Water Management and Green Zones of Madrid City Council 2023) and used mobile phone applications such as PlantNet and "Un alcorque, un árbol".

Flowering phenology (pollen calendar) of the main plant species used by the common wood pigeons in the city of Madrid was estiamted using data from Red Palinocam (https://www.comunidad.madrid/servicios/salud/aerobiologia-polen-esporas#red-palinocam).