Just-released video narrates the first two years of the hawk story at The Franklin Institute.
The Red-tailed Hawk (Buteo jamaicensis) is the most common hawk in North America. It is a large bird with a broad, red tail. The female is usually larger than the male. It appears that a male and a female are co-constructing the nest at The Franklin Institute. Red-tailed Hawks are monogamous, meaning that a hawk will choose one mate and stay with that mate for life.
Philadelphia provides a suitable year-round habitat for Red-tailed Hawks. They can be found in open areas with elevated perches where they sit and watch for their prey. They are meat-eaters and feed on small to medium-sized mammals and birds. In an urban area such as Philadelphia, that would certainly include rodents, although these particular hawks are most commonly observed to be feeding on pigeons.
The Red-tailed Hawk builds its nest in a tall tree or other elevated perch. The nest is a circular assembly of sticks and twigs, lined with softer pieces. It appears that The Franklin's hawks have used newspaper scraps and feathers to soften their nest. Tree bark and leaves are also known to be used in nesting.
Red-tailed Hawks will lay a clutch of two to four eggs in March or April, depending on climate. (A clutch is the collection of eggs, kind of like a "litter" in other species.) For Philadelphia's latitude, the eggs are likely to be laid in mid-March.