Wednesday, June 21, 2017

Summer Solstice: June 21st!



by Anna Autilio
Environmental Educator

Happy Summer Solstice!

Earlier today, the sun was at its highest point in our sky--the highest it will be for the rest of the year. Today, June 21st, is the longest day of the year, at just about 15 hours and 33 minutes. Perfectly timed to make the most of the beautiful weather!

The Salk Institute, during a spring equinox--different from a solstice!
by Joe Belcovson
What is a solstice? The words solstice itself comes form the Latin words sol (sun) and sistere (to stand still). Many cultures, from Native American groups to the ancient Egyptians, have holidays or rituals surrounding the summer solstice. In some places it is celebrated as the beginning of summer, others as the midpoint or "midsummer". There is even some architecture that takes advantage of the sun's position during the solstice, creating views that can only be seen once per year.

Solstices occur on any planet orbiting a star, when one of its poles is most inclined towards that star. Since the Earth's axis is tilted with respect to the sun about 23.4 degrees, during the summer solstice, the northern hemisphere is dipped more dramatically towards the sun's rays than at any other point in the year. On this day, if you are standing on the Tropic of Cancer (a latitudinal line at roughly 23 degrees North, going through Mexico, Egypt, Saudi Arabia, and India) the sun will traverse the sky directly overhead. By comparison, an equinox occurs when day and night are of exactly equal length: in the fall and the spring.

Image result for summer solstice

A common misconception is that the Earth is closest to the sun during summer--not true! It is in fact farthest away at this point. Though summer is hot and winter is cold, these temperatures have everything to do with the amount and angle of daylight experienced by different parts of the Earth each season, and nothing to do with distance to the Sun.

However, it's not the summer solstice everywhere on the planet. Today is the winter solstice in the southern hemisphere, and places like Chile, Australia, and South Africa are experiencing the shortest day of the year, as the Earth tilts them away from the sun by 23.4 degrees. Ushuaia, a city in far southern Argentina, will experience just 7 hours of sunlight today.

What are you planning to do with your extra moments of daylight today? Let us know!


Monday, June 12, 2017

The Red-tailed Hawk with Bald Eagle Parents

by Anna Autilio
Environmental Educator

Amidst the news stories this week is the curious tale of a nestling Red-tailed Hawk in British Columbia, Canada. Why is this little bird, of the most common hawk species in North America, the subject of headlines across Canada and the United States?

Nestling Red-tailed Hawk (front, left) with Bald Eaglets. NPR.

A young Red-tailed Hawk has been spotted among three eaglets in a nest at the Shoal Harbor Migratory Bird Sanctuary, and is being fed and cared for by the Bald Eagle parents. How did a baby Red-tail, unable to fly, get into a Bald Eagle’s nest? There are a few possibilities, but a likely scenario involves the Bald Eagle’s opportunistic, predatory tendencies. Imagine a nest of hungry, growing eaglets that need to be fed. Nearby is the nest of another bird, whose young are fluffy, defenseless, and look tasty to boot. Now imagine the adult eagle carries one of these back to the nest to feed its own young.

Ordinarily, that would be where this story ends, but in this instance, it seems the baby Red-tail survived, and even started begging for food in its new home. The Bald Eagle parents saw an additional mouth to feed…and start supplying it.

Why can the eagles not recognize the Red-tail doesn’t belong? It may be because they are wired not to. Killing prey near or inside the nest carries a serious risk that the eagles will cause harm to their own young. The balance between the risk of harming your own and providing a bit of extra food to an intruder often lands in the favor of the interloper. 

Brown-headed Cowbird egg (speckled) with Eastern Bluebird eggs.
This is often how parasitic nesters get away with what they do—dumping eggs in other birds’ nests, and leaving the host parents to care for the hatchling. A bluebird could try its best to identify the cowbird egg in its clutch, but the risk of making a mistake and kicking out one of its own eggs is greater than the risk of caring for the growing cowbird—at least, in the short term.

The unwillingness of raptors to kill prey near their own nests has other side effects as well. Occasionally, smaller songbirds will nest very close to or within the same structure as a raptor’s nest. This seems extraordinarily risky—shouldn’t the Goshawk parents eat the sparrow hopping around near their babies? Well, not if they don’t want to accidentally talon those babies in the ensuing fight. In exchange, smaller birds nesting near raptors gain protection from other types of predators that the raptor will fend off. 

 
A European Starling (far left) inches from a Red-tailed Hawk nest.

What is the risk of imprinting for the Red-tail? Probably high. When any young animal is growing up, they gain knowledge from their parents. For some, the parents themselves are a crucial component—they let the young know what species they are. Usually, everything goes smoothly: mallard ducklings are raised by adult Mallards, and later learn to seek out other Mallards. But occasionally, a mismatch occurs. The duckling is raised by a human, and decides it is a human. Imprinting is irreversible, and it is cause for a rehab patient to be deemed non-releasable. We cannot know what is going through the mind of this young Red-tail as it looks up at its Bald Eagle parents, but it may be making important decisions that will affect its success later in life.

Is there a risk the Bald Eagles will suddenly turn on the Red-tail, and treat it as the meal it was meant to be? Of course, but given the facts above, it seems unlikely. At least, unlikely until the Red-tail fledges, physically leaving the nest under its own power.

We’re hoping the best for the little guy and his adoptive family. Please share your questions and thoughts below!