How costly is clutch formation in the Audouin's Gull Larus audouinii?

Abstract

During the Audouin's Gull's breeding season at the Ebro Delta in 1993, 24 fresh eggs from eight three‐egg clutches (modal clutch‐size) were collected at the peak of the laying period. Eggs were processed to obtain formalin‐fixed yolks, which were halved and stained using the potassium dichromate method. Digitized images of the yolks were examined to assess the daily rates of yolk deposition. We used these data in combination with egg compositional analysis to build a model of energy demands during the formation of an average clutch in Audouin's Gull. To show how the different parameters of clutch formation affect the daily energy investment peak, we performed a simulation analysis in which the rapid yolk development (RYD) period, the follicle triggering interval (FTI), the laying interval (LI) and the albumen synthesis period (ASP) were allowed to vary simultaneously. In our sample, the mean RYD period was seven days with a range from six to eight days. There were no significant differences in yolk volume among eggs in a clutch, but albumen volume was significantly smaller in third eggs. According to our model the albumen synthesis of the a‐egg coincides with the energy demand peak for clutch formation. This peak represents an increase by ca. 42% in female energy requirements. Values obtained from the simulation analysis showed that only the ASP of the a‐egg and the RYD durations of the second and third follicles produced noticeable reductions in peak energy investment. We predict that in gulls, whose laying intervals seem to be kept constant, significant increases of the durations of the RYD periods of second and third eggs, or even significant reductions of yolk size of these eggs, may operate simultaneously to match the energy demands during clutch formation to the prevailing food conditions.

Individual changes underlie age-specific pattern of laying date and egg-size in female common terns Sterna hirundo

“…The detected increase in the egg-size with age in young common terns might be related to a maturation process (Robertson et al 1994) or to an improved capacity to acquire certain nutrients for the eggs that might limit egg-size. Increasing evidence is accumulating that proteins or certain aminoacids rather than energy may constrain egg-size (Bolton et al 1992; Ramsay and Houston 1997; Ruiz et al 2000). In our colony, the diet of early-laying terns showed a higher proportion of marine prey, higher in energetic value and protein content than limnetic prey, compared to late-laying terns (Wendeln 1997).…”

Maternal Effects in Relation to Helper Presence in the Cooperatively Breeding Sociable Weaver

“…An energetic model based on Audouin’s Gull’s Ichthyaetus audouinii three-egg clutches showed that, for egg formation, the energy-demand peak takes place during the formation of the first egg’s albumen when yolk formation is already completed but females still have to complete forming the yolk of the two following eggs [83]. Therefore, the best way for females to save energy during egg formation is to reduce investment during this peak which can occur by reducing the amount of albumen for the first egg and yolk deposition for second and third eggs [83]. This model explains why first eggs’ yolk mass is much less variable than yolk mass of second or third eggs which is also the case in sociable weavers [74].…”

Early maternal, genetic and environmental components of antioxidant protection, morphology and immunity of yellow-legged gull (Larus michahellis) chicks

“…, 2000). Conversely, females may tune allocation of materials to the albumen, which is accumulated over a short time interval before laying (Ruiz et al. , 2000), and larger inter‐egg intervals may allow larger accumulation of albumen material.…”