Gebruiker:Kweetal nl/Kladblok.Actitis m

Breeding

Breeding grounds are chosen based on various environmental factors, but tend to be in the proximity of bodies of water that offer some coverage from vegetation. Successful breeding sites may be used repeatedly until either the site becomes physically unsuitable (from overgrown vegetation or flooding) or predation becomes too severe. The females usually arrive at breeding grounds before the males do and establish their territories. Males arrive to breeding sites later, but it is uncertain whether or not they will arrive to the same breeding sites that some females have chosen. The search for mates amongst female spotted sandpipers is much more competitive than finding potential mates is for males.

During each summer breeding season, females may mate with and lay clutches for more than one male, leaving incubation to them. This is called polyandry. Male spotted sandpipers take care of the offspring, both before and after the offspring hatch. They will incubate their eggs for about 20–23 days. Male parents of first clutches may father chicks in later male's clutches, probably due to sperm storage within female reproductive tracts, which is common in birds. Females that fail to find additional mates usually help incubate and rear chicks. "Prior to incubation, blood plasma concentrations of testosterone and dihydrotestosterone are substantially higher in males than in females" and these levels plummet 25-fold in males as incubation proceeds. Additionally, mated females have testosterone concentrations that are 7 times higher than those of unmated females. Due to their polyandrous behavior, spotted sandpipers tend to produce more offspring compared to other species of sandpipers.