On average, while not necessarily longer, female ospreys are 20% heavier than males and have a wingspan that is 5 to 10% greater. Female ospreys also often have darker plumage and a more defined necklace than their male counterparts.
Ospreys breed once yearly. The breeding season lasts for approximately 2.5 to 4 months. Two to four eggs are laid over a period of several days, each 1 to 2 days apart. Both the male and female incubate the eggs, which hatch after approximately 40 days. Because incubation starts when the first egg is laid, the eggs hatch asynchronously in the order in which they were laid.