Editing Western grebe (section)

==Reproduction and survival==
[[File:Western grebes and young (15762964143).jpg|thumb|alt=Two western grebes, one in a nest, another approaching the nest. Both grebes are carrying baby grebes on their backs.|Western grebes nesting with young]]
The clutch size decreases as the mating season progresses, meaning if the mating is done at the last of days in mating season, the number of offspring produced is smaller.<ref name="Robison, K. M. 2014">Robison, K. M., Anderson, D. W., & Robison, R. E. (2014). Brood Size and Nesting Phenology in Western Grebe (Aechmophorus occidentalis) and Clark's Grebe (Aechmophorus clarkii) in Northern California. BioOne, 38(1), 99–105.</ref> However it is also stated brood size of nests that hatched later in the season is larger than those from earlier, which contradicts previous findings.<ref name="Robison, K. M. 2014"/> This may be due to ecological constraints. Ecological constraints also pressure the young, and this may lead to siblicide in the first weeks after hatching, which may explain the brooding differences.<ref name="Robison, K. M. 2014"/> Also, Western grebes are sensitive to humans, such that when there is human disturbance near them, the parents leave their nest, leaving their unhatched eggs vulnerable to attacks by predators. This shows the predation or even the seemingly threatening acts result in a decrease of reproduction and survival of the young.<ref>Seattle Audubon Society (n.d.). Western Grebe. Retrieved from [http://birdweb.org/birdweb/bird/western_grebe].</ref> Because they are so sensitive, there have been restoration efforts to rebuild the Western grebes' native habitats, so that they have greater opportunity to reproduce and raise their young without disturbance or threat. The number of Grebes has been slowly declining in the last two decades, not only because of predation, but also because of [[habitat destruction]], with oil spillage being one of the major causes.<ref>Mills, K. L., Gaydos, J. K., Fiorello, C. V., Whitmer, E. R., De La Cruz, S., Mulcahy, D. M., … Ziccardi, M. H. (2015). Post-Release Survival and Movement of Western Grebes (Aechmophorus occidentalis) Implanted with Intracoelomic Satellite Transmitters. Waterbirds, 39(2), 175–186.</ref>