Eastern Screech-owl Pellet Examination

Sometimes you find other things in Waterfowl Nest Boxes, for example, Eastern Screech-owl pellets.

Eastern Screech-owls (Otus asio) reside in the state of Connecticut throughout the year.  However, they are observed infrequently on the White Memorial Foundation property because we do not have large quantities of breeding habitat.  Eastern Screech-owls are most often observed at White Memorial in the autumn and winter months when these owls tend to move around more.   The owls are searching for habitat that offers food and adequate cover from the extreme weather and predators during the winter.We received at least two reports of Eastern Screech-owl observations on the property in December 2012 to January 2013 by birders who visited the property. You can review these observations at e-bird.

We found Eastern Screech-owl pellets while checking the Waterfowl Nest Boxes on the property this year.  The pellets were observed on top of the waterfowl nesting material and since waterfowl and Eastern Screech-owl breed at approximately the same time of year, it suggests that the owls used the boxes after the breeding season.  Learn how owls produce pellets.   A total of 3 boxes had pellets.  The nest box in Hammill Marsh (box #5573) had 4 pellets, #3236 in Pine Island Ditches had only 1 pellet, and the box at Ice House Marsh (#8054) had a total of 5 pellets.  Locate these boxes in the map at the bottom of the page.  The habitat around these boxes varies widely.  Hammill Marsh is primarily a herbaceous marsh north of Little Pond.  Pine Island Ditches are located north of Bissell Rd. and east of Duck Pond.  Pine Island refers to habitat because of the conifer trees and shrubby marsh but there are large herbaceous marshes to the north named Mallard Marsh.  Ice House Marsh is a small shrubby-herbaceous marsh surrounded by mature forest and a small mowed field where the old Ice House ruins are located.  This area is located north of Bantam Lake and east of North Shore Rd. 

We expected to see different species of prey because of this habitat variability. Will Hafey and Heather Williams, Wamogo Regional High School students, dissected the pellets to examine what these owls were eating while using the property.  The pellets found in Hammill Marsh and Pine Island Ditches had a total of 2 Meadow Voles (Microtus pennsylvanicus).  Meadow Voles commonly inhabit open heraceous habitats like fields, marshes, and even many people's backyards.  The Ice House Marsh nest box had pellets with the greatest abundance of prey items and two different species.  These pellets yielded at least 6 White-footed Mouse (Peromyscus leucopus) and 1 Southern Flying Squirrel (Glaucomys volans).  These prey species are abundant along forest edges and mature forests.  We can differentiate the prey species by examining the skull, teeth, and long bone characteristics.  We count and match mandibles and skulls, as well as long bones in the limbs and pelvic girdles to determine how many of each species were eaten.  Review the photos below to see the similarity in size and other characteristics of the evidence we use to determine this diet analysis of Eastern Screech-owls on the property.

Meadow Vole rostrum, mandible, and a couple long bones.

White-footed Mouse mandible and few long bones.

Southern Flying Squirrel long bones.

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