Purple Martin eggs and babies

Here is the nest of a pair of Purple Martins. The first photo shows the eggs during incubation, each egg just under an inch in length. The second shows the baby martins the day they hatched. I've darkened the image around the birds so they might be more easily seen. Also, the egg in the nest with the birds has been placed there with Photoshop software, to show sizes side by side. The young birds are naked, blind, and helpless, in addition to being very small and, well, ugly. Their eyes open a few days after hatching. They will be mature enough to leave the nest about four weeks after hatching. Lisa Rock, a friend who tends the martins at her Ohio home, and who provided the photos, says the only problem she sees at the moment is a lone male House Sparrow determined to compete for the nesting sites, occupied or not. Sparrows will puncture eggs and kill the young of other cavity-nesting species. (House Sparrows are non-native, invasive species, and, in my opinion should be treated like any other invasive.)