Nest survival models indicated that habitat best explained nest predation likelihood, whereas edge, annual, and nest age effects were unimportant.
First, we reduced any confounding effects of nest age because all nests were found and observed starting on day 1 of incubation (see Dinsmore et al. 2002 for a discussion on nest age as a confounding effect).
We also retained the date of initiation of the incubation process (Julian date) and the nest age in the model (Table 2).
It is also plausible that the relationship between DSR of nests and nest age could be a function of predators cuing in on the nest due to olfaction from the female (Storaas 1988) because more odor will be emitted and bound to nest substrates (Conover 2007) the longer a female remains in one area (i.e., nest site).
Other researchers hypothesized that DSR of nests would be lower in the early stages of incubation because vulnerable nests would be depredated earlier (Klett and Johnson 1982; Coates and Delehanty 2010); thus, we incorporated a time-dependent covariate (e.g., nest age) into models.
DSR was associated positively with the Julian date (Figure 4a), percentage of shrub cover (Figure 4b), distance to wells (Figure 4c), and distance to mesic habitat (Figure 4d), but was associated negatively with nest age, distance to roads, and maximum wind speed (Figure 4e).
Egg predation rates of the American white ibis decline with nest age owing to increased nest attentiveness by the parents, especially during the last week of incubation.
The nest age when manipulation occurred (hereafter nest age; days ± SE; 4.65 ± 0.42 days) was determined relative to the clutch completion date (day 0).
Fecal samples were inspected to estimate their likely time of deposition, whereas night nests age was estimated according to a leaf decay index [ 58].
"When you enter a different chapter or encounter new hurdles -- marriage, divorce, kids, empty nest, aging parents -- your sense of self can become disorganized," she adds.
