In addition, increasing adult survivorship via bycatch reduction consistently yielded greater increases in λ than reducing pre-fledging mortality for all models considered (Figure 5A).
A Danish study showed that predation by mammals, especially red foxes, was an important cause of mortality in newly fledged young, with 36% dying between fledging and independence.
The mortality risk increased with fledging date from 14% in April to more than 58% in June, and increasing predation of late broods may be an important selective agent for early breeding in this species.
However, as Airam Rodríguez of Estación Biológica de Doñana CSIC explains, there is a more heartwarming side to this story " To mitigate light pollution-induced mortality rescue campaigns are conducted every fledging season by local governments or NGOs asking for implication of the general public.
Body size at fledging is known to predict post-fledging survival in birds [39], [40].
While there have been documented detrimental effects on the growth rates and fledging masses of chicks, it is still unclear what levels of mortality are caused by plastic ingestion [17] [20].
Our analyses are based on birds surviving to fledging, and our interpretations assume no morph-specific biases in prefledging mortality.
However, mortality is very low between 25 days old and fledging in this species, and thus survival at 25 days old is a reliable estimation of survival at fledging (unpublished data).
It was not possible to analyze growth over time using repeated measures ANOVA or GLMM because extensive mortality in one of the groups (>80% prior to fledging in unlined, heavily parasitized nests) made sample sizes very uneven over time.
After fledging and leaving the care of their parents, young sparrows have a high mortality rate, which lessens as they grow older and more experienced.
On average, birds fledged 94 days after hatching and left the nest 95 days after fledging.
