WPBO Owls Fall 2010: Another Great Spring For Owls

Thursday, June 4, 2009

Another Great Spring For Owls

Before we start the summary of this spring's owl banding, we have to thank all of you who supported the 2009 WPBO staff birdathon. Your support increased 300% over last year, and over $6,000 was raised for the summer owl research! With the additional $2,500 we received in grants and private donations, we have raised the full dollar amount necessary for the summer season. This is the first time we have been able to accomplish this, and we are extremely grateful. Thank you, thank you, thank you!

The spring owl banding season came to a close on the night of May 29. With 773 owls of 7 species banded, and the recapture of another 34 owls that had been previously banded, it was another productive season. The banding results listed below once again demonstrate the importance of the role that Whitefish Point plays in owl migration.

548 Northern Saw-whet Owls

73 Boreal Owls

138 Long-eared Owls

1 Short-eared Owl

4 Great Gray Owls

7 Barred Owls

2 Great Horned Owls

While the overall number is down from the 1192 owls banded last spring, it was a very successful season. The reason for the drop off is that Saw-whets had a poor breeding season last year. The number of young Saw-whets banded dropped from 673 last spring to just 149 this spring. While the number of young Saw-whets was down, more adults were banded this year. The 139 Long-eareds banded represents the 3rd highest season total for WPBO. We had hoped for a better Boreal season, but 73 is a very respectable number. The peak night occurred on May 1st, on which night 25 Saw-whets, 12 Boreals, 20 Long-eareds, 1 Short-eared, and 3 Barreds were banded, and a Great Gray was seen.

Whitefish Point is such an amazing place. This season's results simply reinforce the fact that the owl migration that occurs here is one of the most significant and diverse in North America. In addition to the 7 species that were banded, Snowy Owls were also observed several times this season. We will never forget the sight of two Snowies sitting together at the tip, or of one sitting in a pine at the entrance to the owl road. Given the variety of owls this spring, it is somewhat surprising that no Northern Hawk Owls were observed. We thank all of you who visited for your enthusiasm, encouragement, and support. We are currently enjoying the opportunity to walk among the living for a while before going nocturnal again during July and August. Don't forget that Sarah will be running the evening owl programs during the summer season.

Great Gray, Boreal, & Saw-whet Owls

A Boreal Owl's feathered feet

Long-eared & Short-eared Owls

Barred Owl

Great Gray Owl

A Great Gray's underwing

Great Horned Owl

Snowy Owl

1 comment:

Anonymous said...: We feel so privileged to have been there May 1st, what a night! Great job Chris and Nova.
Thanks,
Bruce and Wanda; June 9, 2009 at 1:45 PM

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Our New Summer Owl Study

During the summer of 2006 WPBO conducted an exploratory owl banding research project at the Point. Our project ran 3 weeks, and our efforts resulted in the capture of 208 owls; 206 Northern Saw-whet Owls (NSWO) and 2 Long-eared Owls. Of the 206 NSWO captured, 200 were juvenile birds. While the spring and fall migrations of NSWO have become increasingly well studied across the continent, these results represent the first documentation of a significant concentration of juvenile NSWO during the post-breeding period.

Thanks in large part to generous donations made by two individuals and pledges to the spring staff birdathon, we have been able to continue and expand this study during the summer of 2007. We began on July 1st, and as of August 10th we have banded 542 owls; 539 NSWO and 3 Long-eared Owls. As in 2006, the majority of the NSWO we have banded this summer have been juveniles.

In addition to the regular data we collect on all owls, we are visually accessing fat stores and muscle mass on all of the juveniles. Among North American owls only NSWO and Boreal Owls have a juvenile plumage that is significantly different from adult plumage. The juveniles begin actively molting out of their juvenile plumage and into adult plumage during our study period. Detailed descriptions of the molt progression on each juvenile have been collected.

Owl banding Spring 2007

Several changes were made to the spring owl banding protocol in 2007. These changes were made in an effort to increase our captures, thereby increasing our data base and our knowledge of the owl migration at Whitefish Point. Owl banding data collected by WPBO during previous springs clearly demonstrated that the Saw-whet migration at Whitefish Point was already at its peak during the 1st week of April. Therefore, the start date of the spring owl research was moved up from the previous start date of April 1st to March 15th. Audiolure was also introduced to the spring owl research for the first time. Audiolure is simply the practice of broadcasting a recording of an owl's call to lure them into the research area. This is a technique implemented at every other owl migration banding site that we know of, and has been used during the fall season at Whitefish Point since the fall study began in 1993. It has been documented that this practice increases Saw-whet captures 5-10 fold.
This spring the calls of Northern Saw-whet and Boreal Owls were broadcast. As the data from previous seasons suggested would be the case, Boreals were at the bottom of their irruptive cycle and none were captured. We fully expect that Boreal Owl captures during the next irruption will increase significantly due to the use of audiolure. As for Saw-whets, the changes proved a huge success after just one season. We banded nearly 280 Saw-whets during March alone; the previous high for an entire spring season was 122. Our total captures for all owl species in March was 318, these results are also higher than the total captures of any previous spring season. The chart below demonstrates the effectiveness of the changes implemented in the spring of 2007.

General Information

Whitefish Point Bird Observatory (WPBO) conducts long-term owl migration studies in both spring and fall. WPBO began its oversight of the spring owl research at Whitefish Point (WP) in 1988, and began the fall study in 1993. A summer study was developed during the summer of 2006 when a dispersal of juvenile Northern Saw-whet Owls was discovered within the study area. These WPBO research projects have resulted in the banding of over 7,000 owls of eight species; Great Horned, Northern Hawk, Barred, Great Gray, Long-eared, Short-eared, Boreal, and Northern Saw-whet. This reasearch has established WP as one of the most diverse owl migration sites on the continent.

* Study periods:
Spring: March 15-May 31
Summer: currently July 1-August 31
Fall: September 15- October 31

**During the study periods nets are opened nightly, weather permitting , 1/2 hour after sunset and closed 1/2 hour before sunrise. Nets are not opened during periods of rain or high winds.

FAQs

Why do we band owls?
The owl banding project is the most effective way we have to monitor the number of owls migrating through Whitefish Point. For example, without the owl banding project just 3 Saw-whet Owls would have be documented in the spring of 2007. Through the owl banding project, 750 Saw-whets were banded and 32 that were already banded were caught. Without specific efforts to document the owl migration at Whitefish Point it would go virtually undetected. For more information on bird banding visit the Bird Banding Lab's website, which can be linked out of the WPBO website.

How do we catch and handle the owls?
All of the owls in our studies are captured in mist nets that are made specifically for bird banding. The mist nets we use are 12 meters long andabout 10 feet high. Due to the size difference between species that we catch two different mesh sizes are used. The nets are placed in openings among the trees at Whitefish Point. To help attract the owls into the netlanes audiolure is used. Audiolure is simply the broadcast of an owls call.In spring and fall both Saw-whet and Boreal Owl calls are broadcast, only saw-whet calls are broadcast in the summer. We do not wear gloves while getting extracting owls from the nets or during the banding and measuring proccess. Like many other things, these procedures are more difficult when wearing gloves. Extractions in particular are already difficult and would be virtually impossible while wearing heavy gloves. Yes, we do occasionally get bit or have the birds get us with their talons, and yes it does hurt. To band and weigh the owls they are placed in cans. This is the common practice when banding birds of prey and actually serves to calm the birds down.

What data do we collect?
Each owl is fitted with an individually numbered U.S. Geological Survey band. These bands are issued to federally licensed bird banders by the Bird Banding Lab in Maryland. The main measurments we collect are weight, tail and wing chord length. If the bird has flight feather molt, the molt pattern is recorded. These measurements and the molt patterns help us determine the age and sex of many of the owls that are captured. The data, including the band number is then submitted to the Bird Banding Lab for inclusion in their database.