Two eggs hatched on April 19th and one on April 20th.
After 42 to 46 days, the young begin to leave the nest on short flights, learning to fly and hunt. 42 to 46 days from April 19 would be May 31 through June 4.
Hawks' nests are generally placed in a very high place, so they must have evolved to not step out of the nest. The chicks are mobile within the nest, but if you look closely you can see that their feet and claws are large and powerful from a very early age and cling tightly to the woven sticks of the nest.
One of the three eyasses ('chicks') left the nest at 6:59 a.m. on May 30. Video is available here: youtu.be/hgcieTs3MPs. Looks like he/she may have been blown off the nest. The eyass is now on the roof of Weeks Hall (above the nest). Last year, when one of the eyasses was bl own off the nest (and into a tree below), the parents brought it food. Hopefully we'll ha ve a similarly positive outcome again this year.
Thanks to Mark Berres, UW-Madison Assistant Professor of Avian Biology for the following answer:
The chicks are more than adequately equipped to deal with sun exposure. Many species of raptors, including Red Tailed Hawks, build their nests to deal with sun exposure. Many species of raptors, including Red Tailed Hawks, build their nests in areas that receive little or no shade (e.g. Ospreys). Even Red Tailed Hawks nesting in more natural environments typically place their nest in a more exposed position (quite in contrast to many passerine species that tend to conceal their nests). Why is debated but reasonable hypotheses include 1. thermoregulatory (free heat from solar uptake); 2. physical access (larger birds need more "wing-room" to maneuver); 3. visual enhancement (for predator and/or prey detection).
The birds are not exposed the direct sunlight for extended periods of time, either. They do have access to shade for better parts of the day. But if they do get too warm, their physiology is equipped to deal with the heat. Body heat can be dissipated from the skin surface, transferred by conduction to cooler objects with which the bird is in contact, and by convection to the surrounding air. This is accomplished by increasing blood flow to the blood vessels in the skin. Behavioral changes will also occur. If too warm, the chicks will move apart from each other and spread their wings to promote convective heat loss by increasing the surface area of the body. Standing upright also employs the feet and legs as important heat dissipating structures. The chicks may also "pant" to increase the rate of evaporative water loss to augment heat dissipation. During panting the beak is opened fully and the tongue is lifted forward from the lower mandible (note that this is not the same as gular flutter, a cooling method practiced by other species of birds).
In general, temperatures up to around 95F or so can be tolerated. Note that there is excellent convective cooling potential as it is generally windy up on the ledge.
Even birds that nest in cavities (e.g. tree holes) and elsewhere in so-called protected areas are not immune to the effects of heat stress, including these hawks. Heat-induced mortality is possible and in fact not uncommon in birds, particularly young chicks.
As to the question of "Can you provide some shade" ... There is good reason not to: first, doing so would like incur significant disturbance for both the chicks and parents alike. It would be dangerous to even attempt it, as the parents would vigorously defend their nest.
Second, the mere presence of the umbrella would likely cause chronic stress for the birds. There are no nylon umbrellas that wild Red-tailed Hawks use.
The camera was purchased for a project to record timelapse movies of cloud formations, from the roof of the Atmospheric, Oceanic & Space Sciences Building. It is temporarily on-loan to provide video of the hawk's nest. For the rooftop cloud formation timelapse movies, camera resolution and durability were our primary concerns, which is why the camera does not have nightvision or sound.