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Barred Owl Research - Overview

Introductions

According to the text books, Barred Owls are supposed to need large stands of old-growth forest to survive. Yet the species is abundant throughout the older suburban neighborhoods of many cities in the southeast. Intrigued by this apparent contradiction, we initiated a study of Barred Owls in the Charlotte region in the central Piedmont of North Carolina in 1999. One of our initial question, simply put, was whether the books were wrong or have the local Barred Owls simply neglected to read the books?

      Over the subsequent decade four graduate students, a small flock of undergrads, and I have studied Barred Owls in both suburban and rural habitats around Charlotte. Besides figuring out what Barred Owls are doing in this unusual habitat, we compared the natural history of the two populations. Are the city birds reproducing as well as their country cousins? Are territory sizes the same? How exactly do the two habitats compare structurally? Do the city and country birds rely on the same prey species? How far do the young travel when they leave their natal territories?

We began our study in 1999 placing nest boxes for Barred Owls in suburban Charlotte and the surrounding rural areas. We collected our first nesting data in 2000, and banded and radio-tagged our first adult owl in January of 2001.

ALL ENCOUNTERS

Young

204

Post-dispersal young

1

2nd year birds

3

Adults

93

TOTAL

301

Retraps

43

 

The 43 retrappings represented 29 birds. Of these, 18 were retrapped once, 8 two times, and three serial offenders were retrapped three times.

INDIVIDUALS


Adult/no radio

7

Juvenile/no radio

161

Brancher/tagged

11

Nestling/tagged

22

Orphan/tagged

6

Post-fledgling/tagged

2

Tagged adults

49

TOTAL

258

 

Summarizing these totals:

Radio

Band only

Adults

50

7

56

Juveniles

39

162

202

89

169

258

 

Radio-tagged

Rural

Suburban

Orphan

5

1

6

Adult female

9

18

27

Adult male

3

20

23

Nestling/brancher

12

21

33

TOTALS

29

60

89

 

How Encountered

Mistnet

20

Bownet

2

Noose trap

41

Chimney

5

Nest

170

Pre-brancher

2

Brancher

12

Orphan

6

TOTAL

258

 

Morphology

            While processing owls for banding or radio tagging, we measured wing (unflattened wing chord) and tail length and weighed them.
            In Charlotte, female Barred Owls are about 30% heavier than males (means 902g vs. 695g), with wings 4% longer (33.4cm vs. 32.14cm) and tails 3% longer (22.5cm vs 21.7cm) than males. There is overlap in all three measures, but all are statistically significantly (p<.05) different.

Table. Morphology of adult Barred Owls in Charlotte, NC, (mean, standard deviation, N).

Females

Males

Weight (g)

901.8 (92.56, 43)

695.4 (53.80, 35)

Wing (cm)

33.4 (1.07, 32)

32.1 (1.07, 25)

Tail (cm)

22.5 (0.89, 32)

21.8 (0.82, 26)

 

Reproduction

Based on known or estimated hatch dates for 49 nests (Fig. ) and an estimated 30 day incubation period, egg laying in Charlotte begins as early as the first week of January (rarely) with a peak at the end of February and beginning of March, with most eggs laid between the second week of February and the third week of March.