I made repeated visits to determine whether potential breeding sites were used, and then the following breeding statistics were collected for all breeding pairs: breeding date (date of first egg), clutch size (number of eggs/nest), mean egg mass, number of eggs to hatch, number of addled eggs, brood size (number of young/nest), number of young to fledge, and nestling size at 13 d after hatching ([plus or minus]1 d).
I used analysis of variance (ANOVA) to determine if brood size negatively affected productivity (i.e., number of fledged young), nest success (proportion of nests to fledge young), fledging success (proportion of young to fledge), and nestling quality (i.e., mass and size).
Hence, pairs that began with a larger clutch should fledge more young than pairs that began with a smaller clutch when both are given the same number of young to raise (Nur 1986).
Nonetheless, to reduce the probability of biasing my estimates of survival, I eliminated all nests that failed to fledge at least one nestling from the analysis of return.
Under the assumptions that food is limited and costs of reproduction are passed onto offspring, I predicted that both the proportion of young to fledge and nestling quality would decline with increasing brood size.
Finally, a comparison of the proportion of recruits to fledge from different-sized broods was virtually identical to the proportion of nestlings that fledged from each brood size (Fig.
Nestlings in large broods generally took more time to fledge ([bar] X = 32.6 [+ or -] 2.5 d, n = 220) than those in small ([bar] X = 30.5 [+ or -] 1.6 d, n 51, Tukey HSD test, P [is less than] 0.001) and medium ([bar] X 31.2 [+ or -] 2.3 d, n = 64, Tukey HSD test, P = 0.022) broods (Table 4).
High-quality chicks may be expected to grow faster and fledge at a younger age than low-quality chicks (but see Ross and McLaren 1981).
It might be argued that brood reduction occurred in nests where parents delivered less food, and therefore surviving nestlings should be expected to grow more slowly or be less likely to fledge than in unreduced broods.
Our results suggested the possibility of an additional cost to asynchronous hatching: chicks in large ASYNC broods generally took longer to fledge than their SYNC counterparts.