HOW DO WE LOCATE GREAT GRAY OWL NESTS?
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Our strategy for locating Great Gray Owl nests combines several methods during the core of the early breeding season, primarily in March when these owls are most likely to vocalize. We focus on surveying as many likely habitats as we can to maximize our chances of detecting owl activity.
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In-Person Surveys: We conduct field surveys where we listen for calls of the Great Gray Owl. If no calls are detected (which is typical), we perform a callback by broadcasting recorded territorial calls, aiming to elicit a response from owls within their territories.
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Autonomous Recording Units (ARUs): These compact audio recorders, specifically designed for wildlife research, are set up to record throughout the night. Using advanced audio analysis tools, we process the recordings to flag likely Great Gray Owl vocalizations, which we then verify manually. This remote monitoring enables us to cover extensive ground with minimal disturbance. Learn more about the ARUs we use here: owlsenserecorders.com
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Public Information: Sometimes we are notified about owl activity or an actual nest from members of the community. If you know about a nest site or a pair and would like to share it with us, let us know! Keep in mind that owl nests can be sensitive to disturbance, so please don’t publicly share it.
When potential nesting areas are identified by the methods above, we focus our efforts on systematic nest searches. Beginning in April, when females are incubating eggs and remain in the nest, we conduct thorough, on-foot surveys. Moving slowly along transects, we inspect every potential nesting structure, such as large snags and stick nests, that could be suitable for Great Gray Owls. Often the female in the nest is well hidden and we can only see a few feathers sticking out. Occasionally, we are fortunate to hear a faint owl vocalization, which significantly improves our chances of finding an active nest.
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When we do have a Great Gray Owl nest with a cam on it, viewers like you can watch and learn.​​​​​​​ View our live nest cam here or see highlights from previous years at the link below.
© Kurt Lindsay
K E Y T E R M I N O L O G Y A N D B E H A V I O R S
Use this guide to help understand the behaviors we are monitoring for, and what to look for when identifying events. Few Great Gray Owl behaviors are well understood or documented. Our goal is to create a record for this this nest and this pair. Over more seasons and nests, we will be able to increase our knowledge of this species. We’re including some of these known markers, however, to help you anticipate what to expect.
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Prey Delivery
Owl nests employ a strict division of labor with essential contributions from both sexes. Females do 100% of the incubating; this means that she rarely leaves the nest, and usually only at night for brief periods. The male, on the other hand, does all of the hunting for the female and chicks. When he brings prey to the nest, it is called a prey delivery. During incubation, these deliveries may sometimes happen away from the nest. The pair may meet on a branch and she will accept and eat the prey off cam. As chicks hatch and food needs increase, deliveries to the nest will occur round the clock.
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Great Gray Owls are dependent on small mammals, specifically voles. These medium sized rodents will likely make up the majority of prey deliveries, however, other small mammals may be seen. Occasionally, and especially if food supplies are scarce, a bird might appear. If you see a different prey item brought to the nest, please record under 'other' and write-in what it was. Here are the four most commonly observed Great Gray prey:
I D E N T I F Y I N G P R E Y
Pocket gopher
This large rodent is substantially larger than a vole with a fur covered tail. It is known for it's extensive tunneling below ground - systems of tunnels and burrows from which they rarely emerge. The name pocket gopher comes from its cavernous, pocket-like cheeks which are used to transport large quantities of food back to the burrow.
Approx. length: 7 in + 2 in tail
Approx. weight: 200 grams
During a quick prey delivery, ID by looking for noticeably large body with a short tail.
Photo © LeonardoWeiss - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=12937639
Mouse
The small rodent pictured here is a deer mouse, known to invade homes and carry infectious diseases such as hantaviruses and Lyme disease. This tiny rodent likes to nest high in dead trees where they reproduce year round. They are mostly nocturnal and inhabit a wide variety of habitats.
Approx. length: 3.5 inches
Approx. weight: 20 grams
During a quick prey delivery, ID by looking for a tiny body mass, large ears, white belly, and very long tail.
Photo @ The Regents of the University of California, Deer mouse, https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=8175
Vole
In western Montana there are six species of voles. Pictured above is the commonly seen meadow vole - a plump and fairly long rodent with a short tail, light belly, and gently sloping face.
Voles travel above ground through through shallow tunnels in the grass. Their populations experience dramatic peaks and valleys and, in turn, so do many vole dependent owl species.
Approx. length: 4.5 inches
Approx. weight: 45 grams
During a prey delivery, ID by looking for a large body mass and the short tail.
Photo © Needsmoreritalin at English Wikipedia, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=6631649
Chipmunk
Easily identified by contrasting stripes down the back, chipmunks are medium sized rodents with furry tails and upright ears. Their diet is mostly comprised of nuts, seeds, and fruits, which are also stashed and relied upon to get through the winter. Chipmunks are diurnal, or active during the day, and reproduce once a year.
Approx. length: 7 in with tail
Approx. weight: 50 grams
During a quick prey delivery, ID by looking for conspicuous stripes and furry tail.
Photo © Phil Armitage - http://www.philarmitage.net/glacier/glacier08.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=813321
F E M A L E ' S T I M E A W A Y F R O M T H E N E S T
Female Leaves Nest
Females typically only leave the nest at night. During her time away, she may receive a prey delivery, cast a pellet, defecate, or stretch. For the purposes of the survey, the time should be begin the moment she lifts her body off the eggs or chicks, and end when she flies from the nest.
Female Returns to Nest
Similarly, her return begins as soon as she lands back on the edge of the nest, and ends when she settles back on her eggs/chicks.
F E M A L E ' S B E H A V I O R I N T H E N E S T
Female Preening
Owls preen frequently in and out of the nest. Preening cleans and repositions displaced feathers which are critical to flight and temperature regulation. The female will run her beak down the length of the feather in order to smooth the surface, or sometimes appears to nibble her way down. Talons can be used to preen the head feathers.
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Female Checking / Rolling Eggs
Incubating females rotate their eggs frequently, sometimes even moving them to a new spot in the nest. Rolling the eggs ensures that the embryo gets enough albumen. This is a mixture of protein and water that makes up the 'egg white' part of an embryo. It is filled with nutrients necessary to proper development.
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Female Checking Chicks / Fussing
After chicks have hatched, the female no longer needs to roll her eggs, but will frequently check underneath her. Early on, this can be hard to distinguish from eating or feeding, but her beak will not be moving and she will be shifting chicks and nest material.
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Female Panting / Gular Fluttering
Owls do not sweat so use panting to release excess heat from the body. They sometimes pant during times of stress, as well. Panting and gular fluttering both refer to opening the mouth and puffing the throat in and out to cool off.
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Female Eating
When the male makes a food delivery to the nest which is immediately eaten by the female, record this under Prey Delivery > Who Fed > Female. If however, she caches the prey and eats it later, or returns to the nest with prey in her beak and eats it at the nest, record those events under the Female Eating category.
E G G E V E N T S
Egg Pip
A pip is the first sign of hatching which is visible as a small piercing to the eggshell. Pipping refers to the process of breaking open the eggshell using an egg tooth - a small, sharp protuberance on the beak that is used to break through the egg’s hard surface. Strong muscles in the chick’s neck give them the strength needed to do this. Chicks initiate pipping when they are ready to survive outside of the shell and have grown too large to absorb oxygen through the pores of the eggshell. Not long after hatching, the egg tooth falls off. It may impossible to see any pips. Nonetheless, stay on the lookout and watch for behavioral changes in the female. She will hear her chick’s earliest pipping efforts and may show an increased interest in checking on the eggs, as though she is listening intently. Please only record pipping if the egg is visible.
Egg Hatch
Great Gray Owl chicks hatch after about 30 days of incubation in this area. When owl chicks hatch, they are vulnerable and helpless. They cannot walk, see, self-feed, or regulate their body temperature, and are entirely dependent on the care of their parents. They appear pink and white - the combination of exposed skin and partial down covering. Around three days in age, a chick gains the strength to lift its head. When this happens, it may offer the first glimpse of the chick. Prior to this, a hatch may only be indicated by the female’s behavior, or the sight of an eggshell. Shortly after hatching, the female will begin tearing off bits of prey and making visible feeding attempts. A chick may also be seen when she leaves the nest at night. Great Gray chicks hatch asynchronously. This means that they will hatch in the order they were laid, about two days apart.
Female Tossing Out or Eating Eggshell
After a chick fully emerges from its shell, the shell may remain in the bowl and crumble under the activity of the nest; the female may set the pieces to the side; toss them over the edge, or she may eat them. There isn’t a lot of documentation in this area, so we are anxious to record how this female handles the shells. We've created two categories - tossing and eating - but if you observe other behavior with the shells, please record it as 'other' and describe.
H A T C H L I N G E V E N T S
Eyes Open
In general, a chicks's eyes will open around day 10. By this time, you will probably see its fuzzy white head above the nest rim or peeking out from under the mother regularly.
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Nestling Swallows Whole Prey
The female will tear off bits of prey to feed her young from hatching until they are big enough to swallow an entire vole on their own. Watch for this around three weeks.
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Nestling Walking
Young Great Gray Owls won't make their first flight until they are over a month old. Even after they have left the nest, they can only get around on foot. As such, they need to start practicing early and will walk around the nest.
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Nestling Stealing Prey from Other Nestling
Aggressive behavior between owl chicks is uncommon. Although that doesn't mean they won't try to steal a meal from one another!
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Nestling Practicing Flight - Spreading Wings, Flapping, etc.
Wing muscles and coordination begin developing early and need exercise. Wing flapping will become a frequent occurrence and combined with walking around the nest.
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Nestling Defecating
The female will keep the nest clean by eating waste until the nestlings are old enough to defecate over the edge of the nest.
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Nestling Preening
As with the female, preening is an instinct that comes early and will be practiced often. The female will also preen the young, which can be recorded under this category with a note, or under 'other.'
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Nestling Nest Departure / Branching
This nest is located in a tall snag with no branches, so these young owls will jump from the nest onto the forest floor around 3-4 weeks. This may sound dangerous, but they are specially made it. Their still flexible bones will absorb the fall. They young owls will set about looking for branches to climb and places to hide. And this forest - a beautifully undisturbed one - has lots of these! Parents oversee their movements and continue to make food deliveries.
Fledging
While branching, young owls often make their first flight attempts. These are short and clumsy at first but around 7-14 days after leaving the nest they are capable of short flights. “Fledging’ can be defined in different ways but generally refers to the development of enough feathers to sustain flight. Flight practice takes place on the ground after running starts or from branches. For the purposes of our study, fledging is defined as a flight that has both a coordinated takeoff and landing. Hopping up and down, or flights with crash landings are practice runs and not to be considered ‘fledging.’ It is unknown if we will be able to observe these first flights or not.
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Male Feeding Nestling
Around 2-3 weeks the female will begin roosting outside of the nest, but close-by. The male will continue delivering food to the female and she will feed the young. After the young owls leave the nest, and around 3-6 weeks, the female will leave her young. At this point the male will takeover all feeding and care, up to three months.
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Species account / breeding behavior cited:
Cornell Lab of Ornithology, Birds of the World
Great Gray Owl, Stix nebulosa
Evelyn L. Bull and James R. Duncan
Version: 1.0 — Published March 4, 2020
Eggs
A female Great Gray will lay 2 - 5 eggs, depending on prey availability. Incubation is 28 - 36 days, with 30 typical for this area.
Eggs average:
Width approx: 43 mm or 1.69 in
Length approx: 54 mm or 2.12 in
Photo © Klaus Rassinger und Gerhard Cammerer, Museum Wiesbaden - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=37932431
Pipp
An egg pip as seen on an eagle egg at explore's Sauces nest.
Photo © explore.org
Hatching
A newly hatched Great Horned Owl chick. The appearance is very similar to a Great Gray chick.
Photo © Kingston Owl Center, UK
Disposing of eggshells
2017 EF nest female eating the eggshell after a hatch.
Photo © explore.org
2020 cam male at Jim's Place hunting voles in a meadow near the nest.
G R E A T G R A Y C A L L S & V O C A L I Z A T I O N S
Following are the vocalizations listed in the survey. Please listen carefully to each before recording in the survey.
Unless credited, these audio files are from the 2017 EF Great Gray nest. We recommend listening with headphones and turning your volume up.
Female food begging call -
A squeak like call, generally when she is hungry, and gets louder when the male is nearby with food. These calls are often given in a repetitive sequence, for extended periods of time. When recording, you can enter them individually, or time the spacing and record them as, for example:
Start: 07:12:05 End: 07:13:15
Notes: call given approx every 5 seconds during this time.
Female Gwuk Call -
Louder and more bark-like than the begging call, generally only repeated a few times before, during and just after food deliveries.
© Cornell Lab of Ornithology
Female defensive hoots -
A repeated low pitched call that has a slight tremor to it, generally given in response to a possible threat near the nest, or in response to the male territorial hoots. She can also give a more territorial call that has no tremor, single note repeated, slightly higher pitched than the male.
© Cornell Lab of Ornithology
Female agitated hoots -
A higher pitched, lilty call generally heard in response to an a stress or agitation in the area.
© Cornell Lab of Ornithology
Male territorial hoots -
Very low pitched, repeated deep hooting call, generally used as territorial. The male will give three similar hoots as a contact call to the female.
Chitter contact call -
A chattering, trilling call generally heard during food deliveries. The male often starts the chitter call as he approaches the nest. The female begins her chitter call when he comes in with food. She also uses a softer chitter call when she is feeding the young.
Chick food begging call -
A little, high pitched squeak or shriek that gets louder and more consistent as the chick ages.
O T H E R E V E N T S A T T H E N E S T
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Predator at Nest
Almost all eggs and young chicks are vulnerable to predators. This natural nest is located in an area shared with mesopredators like coyotes, foxes, raccoons and skunks; where bears, and occasionally wolves pass through; and where eagles, hawks, and other owls are common. When confronting a threat or predator, owls demonstrate a variety of nest defense strategies: bark-like hoots, distraction displays, or by diving at the threat. It varies among species and between individuals. All of these behaviors are survival strategies. When watching owl live cams, please remember that these are wild animals in nature. Events that occur on cam can be hard to watch sometimes. At the Owl Research Institute, we have a non-intervention policy. Please review this below.
Other - Write in
When conducting research, standardized categories and methods of data collection are imperative to the process and results. But these are just part of the picture. Unforeseen and surprising events will always happen. As such, please make note of events of special interest.
I N T E R V E N T I O N P O L I C Y
The opportunity to be immersed in the lives of wild creatures makes it easy to become emotionally invested in their well-being. This connection is one of the most powerful things about wildlife cameras, but it also makes them difficult to watch sometimes.
At the Owl Research Institute (ORI), our approach to research and monitoring, including situations that occur on camera, aims to reveal and document how natural processes unfold. These are wild animals and we've made a conscious decision to keep ourselves out their lives as much as possible. While immediate intervention might sometimes seem like the appropriate response, it’s important to remember that we often don't have the right answer. There are countless instances of human intervention which have not solved the problem at hand, and in fact, created a whole host of other unintended consequences.
At ORI, we have a non-intervention policy. Exceptions include situations caused by humans. We have, for example, removed fishing line from the beak of an Osprey chick. A chick that is not thriving, however, would not warrant intervention of any kind. Decisions involving a bird in distress often need to be made quickly, with the information at hand.
Sometimes it isn’t entirely clear what is going on and gray areas exist. We will assess, and respond, to each situation as it arises. Like you, we want to see the birds thrive. But, as researchers and cam watchers, our role is not to influence the natural interactions between species and their environments. It is to learn, enjoy, document, and promote the conservation of these animals and their ecosystems.
Thank you for your interest in this project!