Effects of food and ectoparasiteson age of natal dispersal in

burrowing owls

Victoria Garcia

University ofArizona

and

Courtney J. Conway

Photo by D. Hearne

Dispersal and evolution

Inbreeding avoidance

Cooperative breedingMigrationPhoto by John Cocanower Photo by Cagan H. Sekercioglu

Dispersal and populations

Population dynamics Population genetics

Dispersal and fitness

Survival Reproduction

Photo by D. HearneImage by Bobbie Peachey

Natal dispersal

Movement between natal site and first breeding site (Greenwood 1980)

When to disperse?

Natal dispersal timing

disperse as soon as possible

disperse as late as possible

When to disperse?

Burrowing owls (Athene cunicularia)

Vary in age at which initiate natal dispersal (~45 d to >110 d)

Why?

What causes variation in age of natal dispersal in burrowing owls?

Sunny Walter sunny@sunnywalter.com

Methods

Study site

6,500km2 area in eastern Washington

Study population

• Mostly migratory

• 2 cavity nesters

• Cache prey in burrow• Juveniles fly well ~40d

Food abundance natal dispersal?Ectoparasite load natal dispersal?

2 treatments to nests:

mice control

diatom earth n = 17 n = 17

control n = 16 n = 17

Mice supplements

• 50% energetic needs (95g/owl/week)

Flea removal

• diatomaceous earth powder & water solution

• powder for dust baths

Nests treated weekly, 14d to dispersal

Determining dispersal age

• transmittered 67 juveniles

• re-located 3x/week until seen >300m from nest >1 visit

• dispersal age from hatch date

Effect of diatomaceous earth on ectoparasite load

Trapped and banded juveniles

Assigned index of flea load (0-5)

two-way ANOVA for a completely randomized design with factorial treatment

• effect of treatments on dispersal age

• effect of diatomaceous earth on flea load

Statistical analysis

Results and Discussion

Juvenile fate

Sample size by treatment

n = 35

mice control

diatom earth n = 8 n = 8

control n = 9 n = 10

control mice

treatment

60

65

70

75

74

62

Food abundanceP = 0.027

control diatom e

treatment

60

65

70

75

80

63

74

EctoparasitesP = 0.065

control diatom e

treatment

1.0

1.1

1.2

1.3

1.4

Effect of diatomaceous earth on fleas

P = 0.65

1.23 1.1

7

control mice

treatment

0.8

1.0

1.2

1.4

1.6

1.0

1.5

Effect of food supplements on fleasP = 0.019

0 1 2 3 4

flea index

40

5060

70

80

90

63

80

62

87

49

(15) (7) (5) (7) (2)n =

Flea load and dispersal age

P = 0.41

Summary1. Food supplements earlier dispersal

2. Food supplements flea load

3. Flea load dispersal age

4. Diatomaceous earth later dispersal

5. Diatomaceous earth flea load

Future directions

• treatments juvenile weight

• juvenile weight dispersal age

• food supplements number fledged

• local food abundance dispersal age

• diatomaceous earth avian ectoparasites

Acknowledgments• BLM (Spokane), Columbia NWR,

Washington Dept of Fish and Wildlife

• Field crew: Lisa Ellis, Joey Jarrell, Rick Keck, Aimee Mitchell, Chris Nadeau, Emily Sullivan

• Landowners in eastern Washington

• Lab group: Alice Boyle, Katie Hughes, Matt Smith, Allyson Wheelock