Ecology

Danny Stoner
Strawberry Hill Nature Preserve

(3/2020) As winter gracefully comes to an end, many animals wake from their deep slumber to search for food and shed their winter fur. The changing seasons signal a time of high activity for owls. They are finding their breeding territories and getting ready to produce offspring.

Did you know? We have eight owls that can be seen in Pennsylvania. These owls include the Northern Saw-whet Owl, Eastern Screech Owl, Short Eared Owl, Long Eared Owl, Barn Owl, Barred Owl, Great Horned Owl, and the Snowy Owl. All but two of these species typically breed in Pennsylvania, and those are Snowy Owls and Short Eared Owls.

The first owl to start its breeding season is the Great Horned Owl. It determines its breeding territory and makes a nest in January. The Great Horned Owl starts so early because the young take from spring to fall to fledge and leave the nest. During this time, the parents will incubate their eggs, feed their young, and teach them to fly and hunt properly.

Most of our owl species are cavity nesters or nest in old nests made by hawks or other large birds. To raise their young, they must spend most of their time hunting. If they cannot supply enough food for the young, they will not survive, and the pair may not produce another clutch. Therefore, owls must excel at hunting. But what makes owls such great hunters?

There are many physical attributes that contribute to the success of an owl. The position of their ears is one of them. Their ears are asymmetric, meaning that they are not even with each other like ours. This allows them to triangulate where their prey is in the darkness of night. One ear is a bit higher on the head and the other is lower. With this feature, they can sense the height or distance of their prey. Then, combining that with the ability to hear what side of the body the prey is on, they can determine an exact location.

Hearing and finding the prey is only half of the hunt. Once they find their prey, they must catch it. This means they cannot allow prey to hear them and escape. They do this with specialized feathers on their wings. On the leading edge of the feathers, which is the edge facing towards the head, there is a comb-like structure that creates less turbulence when they flap, which allows it to make less noise. Once they are close to their prey, they dive feet first with wings pointed up. They become a missile launching into their prey, without the prey knowing what hit them. Owls are great at keeping the rodent population down.

Most of your backyard owls will be Great Horned Owls and Barred Owls. These species are both edge species, meaning they can be found along tree lines. If you are in a development with surrounding woods, or live near a farm with forest around it, you are likely to have one of these owls near you. Both owls like to roost in coniferous trees during the day to hide from the bright sun or weather as they sleep.

If you are hoping to catch a glimpse of one of these common owls, try going out at night to determine the direction their calls are coming from. Then, during the day, you may notice a group of birds "mobbing" the owl. Chickadees, Blue Jays, and Crows are known to mob an owl, meaning they dive at them and call at a higher rate, in an attempt to remove the owl from their territory.

Our uncommon owls (or the ones that are hard to find) would be the Short-eared Owl, Snowy Owl, Northern Saw-whet Owl, and Long Eared Owl. The first three owls noticeably decrease and increase in a cyclic fashion for sightings in Pennsylvania. This means that their numbers increase when there is an increase in prey because they can have more offspring and the offspring have a higher survival rate.

When this happens the next year or in the winter, we have an eruption. This is best known with the Snowy Owl. When the number of offspring is high because of an increase in food, or lemming, the Snowy Owl has to travel farther to find food in the winter since most of the prey was used up during the breeding season. Saw-whet Owls depend on the voles and other small rodents in the boreal forest for their increase in numbers, and the rodents depend on the cones that fall from the evergreen trees, such as spruce and pine. The more cones that fall means the more offspring for the rodent.

Rare Owls that come to Pennsylvania, such as the Snowy Owl and Short-eared Owl listed above, are here only to forage. These are amazing birds to see as they only arrive in winter. However, to see these owls we must treat them with respect, just like any other bird. Bird ethics around owls is not as forgiving as other species, especially for the Snowy Owl. When one appears in Pennsylvania, there is a lot of commotion and people going to see them. Some get a bit too excited and get too close to the bird.

We must remember that they are here in an eruption year as I mentioned above. There was not enough food up north, so they came down here in search of food. If people get too close to it one after another and chase it away from its hunting territory for the winter, the owl must search for a new territory. Searching for new territory will take time, costing it energy and fat that it needs to survive both the winter and the flight back up north. Remember to keep your distance so you do not disturb the owl.

If you are still reading and wish to learn more, I encourage you to join Strawberry Hill for a variety of upcoming bird-themed programs. Beginning in April, Strawberry Hill will be hosting a 3-part birding series called Birding 101. This series will help participants develop the skills needed to grow from a novice birder into the pro you want to be!

We will start at the basics and conclude by testing your new birding skills in the field. Develop skills ranging from understanding what weather conditions are best for birding, to identifying birds by their movement. You will also get to meet Strawberry Hill’s resident barred owl, Strix! This three-part intensive series will run Saturday mornings from 9 -10:30 a.m. on April 18, April 25, and May 2. No prior experience is necessary. The series is designed for birders ages 16+.

This class is filling quickly and limited to the first twenty bird-nerds. Please visit our website, StrawberryHill.org, or contact the office at 717-642-5840 to learn more and reserve your spot.

On Saturday, May 23 at 7:30 p.m., Strawberry Hill will be hosting an Owl Prowl with the hopes of getting you close to an owl in its natural habitat. Strawberry Hill has Barred Owls on both sides of the road that will talk to each other during the day and at night. We will highlight the other noises you may be hearing during the night hike. Before the hike starts, there will be an informational section where you will learn about the owls you may hear or see, and ethics when looking for owls at night.

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