Habitat Selection of the Lesser Spotted Woodpecker (Dryobates minor) across Seasons and Scales

Abstract

Habitat specialists are particularly vulnerable to habitat loss and disturbances because they are adapted to a narrow range of ecological conditions and food sources. The lesser spotted woodpecker is closely linked to attributes of deciduous forests that are negatively affected by intensive management. This is because it is specialised in foraging on wood-living insect larvae found in thin dead branches from living trees, and forestry operations often remove dead wood and large trees, which are the ones providing higher quantity of dead branches in the crown. In this study, I aim to increase our understanding of the specific habitat requirements of this species at different temporal and spatial scales. I used location data of individually tracked lesser spotted woodpeckers in a hemi-boreal region of southern Sweden. Seasonal changes in habitat selection at the landscape scale were studied with a use-availability approach. The effect that sampling availability at different scales may have on the estimates of habitat preference was also assessed. At a finer scale, habitat preferences were studied for the pre-breeding season, which is the most critical time for the species in terms of food requirements and energy demand. I used a zero truncated negative binomial model to determine the influence of available preferred tree species on the intensity of use of forest stands within the spring territory. At the landscape scale, the species showed a strong temporal consistency in its preference for deciduous forests, but it was slightly stronger in spring than in winter. In winter, there was a slight increase in use of coniferous forests which likely reflects that the required food intake is lower at this time. Within the spring territory, the intensity of use of a forest stand significantly increased with the availability of dead branches from living alders and limes, two of the preferred tree species for foraging in the study area. I concluded that habitat use at the territory scale was also dependent on food availability, as the preference for high density of alders was only significant the years it held higher prey densities due to mast-flowering patterns. On the basis of these findings, I suggest management measures to improve and preserve the habitat quality of this species in southern Sweden.

Popular Abstract

The loss and degradation of habitat is one of the greatest threats to biodiversity across the world, and species that are adapted to a narrow range of food sources and ecological conditions are particularly vulnerable. The lesser spotted woodpecker is negatively affected by the transformation and alteration of the deciduous forests it inhabits. This is because forestry operations often remove dead wood and large trees on which the species relies to feed and nest. The lesser spotted woodpeckers mostly feed on small insect larvae that live in thin dead branches attached to living trees and normally nest in standing dead or decaying trees.

In this study, I aimed to increase our understanding of the specific habitat requirements of this species at different temporal and spatial scales. I used location data of individually tracked lesser spotted woodpeckers in a hemi-boreal region of southern Sweden. I studied the seasonal changes in habitat selection at a macroscale, which concerns the placement of the individual’s territory in the landscape. I also assessed the effects of sampling available habitat at different distances. At a finer scale, habitat preferences were studied for the spring season, which is the most critical time of the year for this species in terms of food requirements and energy demand. I looked at how the intensity of use of areas within the spring territory was influenced by the amount of thin dead branches of the tree species that are preferred for feeding.

At a macroscale, the species showed a strong preference for deciduous forests throughout the year, but this preference was stronger in spring than in winter. In winter, there was a slight increase in use of coniferous forests which likely reflects that the species can prioritize areas that are safer from predators, even if they have less food. Within the spring territory, the woodpeckers spent more time in the areas of the forest with higher density of dead branches of alder and lime, which are two tree species with high food availability. The density of oak and birch did not make a difference at this scale, but they were the dominant tree species in the woodpecker territories.

Conservation actions to improve the habitat quality and quantity of the lesser spotted woodpecker should aim at maintaining mature deciduous forests in order to ensure availability of feeding and nesting sites. For example, forest management practices that remove large trees and reduce the canopy cover of deciduous trees such as lime, oak or alders should be avoided. Because the food availability of some tree species may fluctuate annually, it will also be important to promote diversity in tree species composition or the occurrence of different forest types in the same area to promote good-quality habitat in the long term.

Supervisor: Ola Olsson
Co-supervisor: Carsten Kost
Department of Biology, Lund University

• author: Costa i Vilar, Anna
• supervisor: Ola Olsson; Carsten Kost
• organization: Degree Projects in Biology
• course: BION03 20222
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9145094
• date added to LUP: 2024-01-15 17:30:05
• date last changed: 2024-01-15 17:30:05