Non-adaptive territory selection by a bird with exceptionally long parental care

Abstract

High-quality territories are expected to provide greater fitness return for breeding individuals and, thus, are likely to have higher long-term occupation rate in comparison to low-quality territories. However, if environmental and ecological cues used for territory selection cannot reliably predict true territory quality, a mismatch between preferences and fitness may occur. We suggest that this kind of non-adaptive territory selection is more likely in species with long reproductive cycles, as a long time interval between territory establishment and young fledgling should reduce predictability of conditions during the critical stages of brood care. In this study, we investigated adaptiveness of territory selection in a migratory bird with exceptionally long parental care, the mute swan Cygnus olor, which requires over four months to complete the entire reproductive cycle from egg laying to young fledging. For this purpose, we collected information on the long-term (10–19 years) occupancy of 222 swan breeding territories and correlated it with reproductive performance (n = 1,345 breeding attempts) and body condition of breeding adults. We found that long-term occupancy positively correlated with the timing of breeding, suggesting that individuals settled earlier in the attractive, frequently occupied territories. By contrast, we found no relationship between territory occupancy and reproductive output (hatching and fledging success) or adult body condition. The results indicate that at the time of territory selection swans might not be able to reliably assess territory quality, likely due to: (1) exceptionally long period of parental care, which reduces temporal correlation between the conditions at the time of territory selection and conditions during chick rearing; and (2) unpredictability of human-related activities that had a major impact on reproductive output of swan pairs in our population.

Age-related differences in reproductive success support the selection hypothesis in a Mute Swan population

“…Individuals try to maximize their breeding success by choosing the best available territory, but the occurrence of random and unpredictable events during the breeding season can make selection of appropriate territories difficult. In our earlier research, we found no association between territory occupancy and reproductive output (hatching and fledging success) or adult body condition in our study swan population (Włodarczyk and Minias 2016). This means, that some pairs were likely to breed successively in poor quality territories, despite repeated breeding failures, which were often caused by unpredictable human disturbance, such as drainage of fish ponds before the conclusion of breeding activities (Włodarczyk and Minias 2016).…”

“…Swans occupied different habitats, mainly artificial water bodies, such as fishponds, ponds used for recreation and dam reservoirs (Włodarczyk and Janiszewski 2007). The breeding population was stable with no major changes between years during the study period (Włodarczyk and Minias 2016). The majority of swans from our study population are migratory and they normally leave breeding territories in September-October, while they return to breed in January-March.…”

“…Each year, field observations started in March when all potential breeding territories were visited to find territorial pairs. We were able to detect the majority of pairs as the study area contains a limited number of suitable water bodies for swans and the birds do not show fear of human presence (Włodarczyk and Minias 2016). Each territory was visited four times during the breeding season, in April, May, June and August.…”

Human–Wildlife Conflicts in Krakow City, Southern Poland

“…Mute swans are large birds, with the body mass of adult females up to 11 kg and males 13 kg [86], most of the conflict incidents recorded in Krakow with this bird species was AVC having a devastating effect on vehicles involved and their drivers, fortunately non-fatal. Our record is consistent with findings by [87] who found that species with lower reproductive rates, higher mobility, and larger body sizes were more commonly involved in road collisions.…”

Plant invasions alter settlement patterns of breeding grassland birds

“…They postpone nesting until the onset of monsoon rains, typically in July, that trigger growth of grasses and increases in abundance of arthropod prey (Capinera and Horton 1989). This unusually long period between territory establishment and reproduction makes the link between proximate cues used to select habitat and future resources especially important (Włodarczyk and Minias 2016). Because the proximate cues animals use to select habitat are often related to plant structure, settlement responses to invasions may be conditional on structural similarities between nonnative and native plants and the habitat preferences of the species selecting habitat (Steidl et al 2013).…”