VARIATION IN NEST DEFENCE AND INCUBATION BEHAVIOUR IN MOUNTAIN BLUEBIRDS (SIALIA CURRUCOIDES) IN RELATION TO NEST PREDATION
| dc.contributor.advisor | Wiebe, Karen L | |
| dc.contributor.advisor | Chivers, Douglas P | |
| dc.contributor.committeeMember | Clark, Bob | |
| dc.contributor.committeeMember | Dawson, Russell D | |
| dc.contributor.committeeMember | Niyogi, Som | |
| dc.creator | Tkaczyk, Simon Philip | |
| dc.date.accessioned | 2023-09-25T22:18:14Z | |
| dc.date.available | 2023-09-25T22:18:14Z | |
| dc.date.copyright | 2023 | |
| dc.date.created | 2023-08 | |
| dc.date.issued | 2023-09-25 | |
| dc.date.submitted | August 2023 | |
| dc.date.updated | 2023-09-25T22:18:14Z | |
| dc.description.abstract | The predation of nestlings represents a high cost to birds that during the incubation and nestling stage of their development. Consequently, predation likely shapes various aspects of parental behaviour in birds that exhibit parental care. Within any given species, parent birds defend their nests with different levels of intensity. Previous studies have examined several hypotheses for this variation by examining factors such as morphological characteristics of parents and characteristics of the brood, but few have controlled for multiple factors simultaneously. Here I examined a broad range of factors that may influence the nest defence behaviour of Mountain Bluebirds (Sialia currucoides), including morphology of adults (sex, age, plumage colour, body size, and body condition) and characteristics of broods (size, hatch date, and stage of offspring development). An essential aspect of parental behaviour in birds is the incubation of eggs. Maintaining the eggs at a suitable temperature for embryonic development requires time and energy and this must be traded-off with requirements for foraging and self-maintenance. I examined how exposure to a nest predator altered the incubation rhythms of female Mountain Bluebirds and for how long such variation lasted. I studied the intensity of nest defence behaviour and incubation rhythms breeding pairs of Mountain Bluebirds in response to a model nest predator in the central interior of British Columbia. Parental aggression was triggered using a taxidermy mount of an american red squirrel (Tamiasciurus hudsonicus), which is the main predator of eggs and nestlings in the study area. My research had two main objectives: 1) to test whether one sex generally invests more effort in nest defence and whether an individual's investment is related to characteristics of the brood and/or the parents. ), and; 2) to examine whether the incubation rhythms of females change in response to predation risk and how long these changes may last. I found no relationship between nest defence and the morphological characteristics of adults that I quantified, but the intensity of nest defence was positively correlated with the stage of offspring development, clutch size, and hatch date consistent with parental investment theory. Males also defended nests more strongly than females, consistent with the premise of the renesting hypothesis that males have fewer future opportunities to breed and, therefore, are more invested in the current brood. My results provide strong support for parental investment theory and renesting as the primary drivers of nest defence intensity in breeding birds. I found that following exposure to a model nest predator, incubating females reduced the number of times they left the nest, consistent with the hypothesis that they were minimizing the risk of attracting the attention of a nest predator. At the same time, they increased the length of recesses to potentially forage enough to maintain an energy balance. These changes in incubation rhythms were relatively short-lived with the female resuming normal incubation behaviour two days after exposure to a model nest predator. The constancy of incubation (% of time on nest) did not significantly change before or after the predator trial, suggesting that female Mountain Bluebirds place a high priority on regulating the temperature of the eggs even during the threat of nest predation. The incubation rhythms were not influenced by the age and body condition of the female. The external ambient temperature did not affect any aspect of incubation behaviour before exposure to the model predator. However, there was a negative correlation between constancy and ambient temperature after the model predator was presented. My study is among the first to test the parental response regarding nest defence and incubation rhythms to the risk of predation while controlling for multiple factors at the same time. The results of this study suggest that these aspects of parental behaviour were driven primarily by the sex of parent and reproductive value of the brood rather than the morphological characteristics of the parents. My results also suggest that incubating females minimized their activity around the nest following exposure to a model nest predator without significantly altering constancy on the nest. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | https://hdl.handle.net/10388/15059 | |
| dc.language.iso | en | |
| dc.subject | breeding behaviour | |
| dc.subject | plumage colour | |
| dc.subject | nest defense | |
| dc.subject | incubation rhythms | |
| dc.subject | predation | |
| dc.subject | parental care | |
| dc.subject | passerine | |
| dc.subject | Mountain Bluebird | |
| dc.title | VARIATION IN NEST DEFENCE AND INCUBATION BEHAVIOUR IN MOUNTAIN BLUEBIRDS (SIALIA CURRUCOIDES) IN RELATION TO NEST PREDATION | |
| dc.type | Thesis | |
| dc.type.material | text | |
| thesis.degree.department | Biology | |
| thesis.degree.discipline | Biology | |
| thesis.degree.grantor | University of Saskatchewan | |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.Sc.) |