Why do parents produce small broods of offspring that have lower body mass, survival, and lifetime reproductive success? A case study in a long-lived bird

Numerous studies have examined the correlation between offspring quantity and quality, and many have found that the most common brood size is often smaller than broods with the highest offspring quality or production. However, the reasons why these small broods with lower offspring quality are produced, are still poorly explained. Using data spanning 29 years, we investigated the effects of brood size on nestlings’ body mass and the lifetime fitness for those offspring as adults (as proxies of offspring quality) in the Crested Ibis (Nipponia nippon). We also examined the temporal variation of brood size. We found that overall offspring quality increases with brood size and that individuals from broods of three had the highest quality, as quantified by larger body mass, higher adult survival, and lifetime reproductive success. Furthermore, brood size of an individual pair significantly varied across years, and the proportion of broods containing two offspring increased while broods of th..., , Offspring quality: Body mass of nestlings of crested ibis
Survival rate: Marking-rediscover history of crested ibis 
Lifetime reproductive performance: Age of first reproduction, breeding lifespan and lifetime reproductive success
Reproductive performance in each year: The number of nestlings producing by parents in each year, # Why do parents produce small broods of offspring that have lower body mass, survival, and lifetime reproductive success? A case study in a long-lived bird

[https://doi.org/10.5061/dryad.x95x69pjx](https://doi.org/10.5061/dryad.x95x69pjx)

| **file name** | **variable name** | **discription** |
| :------------------------------------------ | :-------------------------- | :------------------------------------------------------ |
| **CI\_body\_mass** | id | bird ID |
| **CI\_body\_mass** | [brood.no](http://brood.no) | the no of broods |
| **CI\_body\_mass** | year | natal year |
| **CI\_body\_mass** | bs | b...