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Department of Biological Sciences
Our research questions, within the broader context of parental care behaviour, addressed four general areas of enquiry:
In gulls and terns that lay a 3-egg clutch, intra-clutch hatching patterns change during the breeding season; clutches initiated early in the season hatch more synchronously than those initiated later ( Figure 5 & Figure 6). In either case, as last-hatched chicks are at a size and competitive disadvantage to their older and larger siblings, these within-clutch conditions produce a feeding hirarchy among the chicks that permits a degree of control by parents over potential conflicts at hatching. When chicks become mobile, disadvantaged chicks are expected to leave the home brood and as they seek parental care elsewhere, put potential foster parents into an inter-generational conflict situation. Our interest is in the patterns associated with these events from the perspective both of the chick seeking adoption and the unrelated parents that might adopt (refs. Morris et al. 1991. Can. J. Zool. 69: 661-668; Brown et al. 1995. Anim. Behav. 49: 321-331).
In seabirds that lay a single egg, the life history patterns and reproductive tactics are expected to be very different from those temperate nesters that lay a multiple-egg clutch. Our long-term objectives for this study which we started in 1985 are (a) to record details of arrival chronology, breeding biology and foraging ecology based on food regurgitated to chicks, (b) to estimate annual survival rates and extent of philopatry, (c) to assess the extent of mate partner and nest site fidelity, and (d) to establish patterns of male and female parental care. Our initial conclusion about the colony was one of stability and predictability based on five years of data during which many of the parameters under study remained relatively constant (ref. Morris & Chardine. 1992. J. Zool. Lond. 226: 65-79). This view was changed with the movement of Hurricane Hugo along a path that held it directly over our study area throughout the night of 18 September 1989. After considering a number of explanations for the loss of about 35% of our colour-banded adult noddies by the 1990 breeding season, and the observation that the colony had about the same number of pairs in 1990 and thereafter as in the years before the hurricane (1985-1989), we conclude that a major stochastic event such as a hurricane can have a drastic effect on partnership combinations and on the structure of a small population (ref. Morris & Chardine.1995. Auk 113: 23-31, Chardine and Morris. 1996. BNA No. 220).
In the past 20 years, the Canadian Great Lakes Common Tern population has undergone a major decline with reductions in numbers of breeding birds at some sites and entire colony desertions at others. Whereas in the early 1970's there were several colonies on Lakes Erie and Ontario with over 1000 breeding pairs and many other smaller colonies, by 1995 only two large colonies remained ( Figure 7). Personnel from the Brock Seabird Lab. manage these two colonies intensively each year by covering the substrate with PVC sheeting in late March, and by visiting the sites daily to disturb Ring-billed Gulls from early April until the terns arrive and settle in late April. These procedures are required as Ring-billed Gulls arrive at the sites and begin egg-laying about one month before Common Terns arrive ( Figure 8). If carried out on a regular and systematic basis, these procedures protect nesting habitat for Common Terns despite the increasing numerical pressure of Ring-billed Gulls (ref. Morris et al. 1992. Biol. Conserv. 60: 7-14).
We have collected data on the foraging activity and patterns of male Common Terns nesting at the "spur dike" colony in Windermere Basin, Lake Ontario (1994, 1995). In each year, we attached radio transmitters to the legs of male Common Terns captured during the last few days of incubation. Over the next two weeks as these birds forage to feed their chicks, field teams obtain radio signals that permit us to identify the foraging locations of each bird. An observer in the blind at the colony identifies the species and size of each prey fish delivered to chicks by the males carrying radio transmitters. These data will allow us to determine whether foraging patterns and prey fish fed to chicks change as a result of the construction of three new artificial islands completed in Hamilton Harbour during the winter of 1995/96. As the islands and surrounding waters create new fish habitat in the harbour, a testable hypothesis is that the terns will take advantage of the opportunity and change foraging locations. Thus, locations and prey types delivered in 1994 and 1995 represent a "pre-manipulation" pattern and can be contrasted with the "post-manipulation" patterns. This project is part of the McMaster University Ecowise Project, funded by the Tri-Council Ecosystem Rehabilitation Program (ref. Quinn et.al. 1996. Can. J. Fish & Aquatic Scil 53 (Suppl. 1): 45-57; Morris et.al. 2001. Ontario Birds 19: 12-25).