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 [email protected]
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