Patterns of nest attendance behavior by breeding birds represent a parent-offspring
trade-off in which adults balance self-maintenance with parental care decisions.
Incubation, in particular, is of interest because adults must provide an environment
suitable for embryonic development through nest-building and contact-incubation.
We evaluated how adult incubation constancy and nest visitation rates varied with
life and natural history traits of temperate and tropical bird species. We found that
constancy did not differ by latitude or with nest survival rate. A strong negative
correlation between incubation constancy and egg mass relative to adult body mass
was present. Birds with low constancy tended to have larger relative egg masses
and higher basal metabolic rate. Because adult incubation constancy is relatively
plastic (i.e., varies with ambient temperature), birds with larger relative eggs may
respond to lower cooling rates rather than direct selection for higher or lower
constancy. We then assessed if rates of nest visitation (trips to nests by adults
during incubation and nestling phases) followed the predictions of the Skutch
hypothesis. Skutch suggested that birds nesting in environments with high levels
of nest predation would reduce numbers of trips to their nests so as to minimize the
risk of visual detection by nest predators. We found support for the basic pattern
predicted by Skutch. We also extended his hypothesis to predict other behavior
associated with nesting, such as responses of parents to intruders at the nest.
Despite apparently early departure from the nest site, adults with higher visitation
rates remained conspicuous around the nest site. Thus, while the flight initiation
distance from the human observer was earlier than expected, conspicuousness of
behavior was associated with nest visitation rate. Finally, we assessed how an
environmental variable, photoperiod, might influence rate of embryonic
development in a wild songbird, Sylvia atricapilla. We exposed eggs throughout
the incubation period to daily photoperiods consisting of 4 hours of light and 20
hours of dark (4L), 12 hours light and 12 hours dark (12L), 20 hours light and 4
hours dark (20L) and a skeleton photoperiod with two 1-hour pulses of light that
framed a 20-hour day. We found that the skeleton treatment group differed
significantly from our 4L and 12L, but not the 20L treatment groups. The skeleton
photoperiod accelerated embryonic development. We suggest that photoperiod
may influence incubation period in wild birds and could account for some portion
of the widely observed latitudinal variation in incubation period of songbirds. We
encourage others to assess how photoperiod interacts with parental attendance
patterns to affect embryonic development. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from March 13, 2013 - March 13, 2015
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37480 |
| Date | 13 March 2015 |
| Creators | Austin-Bythell, Suzanne H. |
| Contributors | Robinson, William Douglas |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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