Nest Microhabitat & Reproductive
Success of the Mountain
White-crowned Sparrow
Brett Klaassen Van Oorschot,
Ondi Crino, and Creagh Breuner
University of Montana
Mountain White-crowned
Sparrows as a study system
Mountain White-crowned Sparrow
(Zonotrichia leucophrys oriantha)
Context for Research
Brand-new fledgling
Question:
Does nest microhabitat affect the
reproductive success of these birds?
Tioga Pass: the field site
(Google 2009)
Background
• Nests are built in a wide range of
microhabitats.
• Over half of all nests fail, but
ecological consequences are
unknown.
Specific Questions:
1. Does the vegetation surrounding
the nest affect fledging success?
2. Does the vegetation surrounding
the nest affect nestling condition?
Background
Belding’s Ground Squirrel
(Spermophilus beldingi)
aka “Sage Rat” or “Picket-pin”
Fearsome and elusive predator
of the Mountain White-crowned
Sparrow.
Background
• Nests are built in a wide range of
microhabitats.
• Over half of all nests fail, but
ecological consequences are
unknown.
Specific Questions:
1. Does the vegetation surrounding
the nest affect fledging success?
2. Does the vegetation surrounding
the nest affect nestling condition?
Nest Searching….
Tioga Pass Meadow
A well-hidden nest
Morphological Measurements
Ondi Crino taking chick measurements
Six-day-old nestling
Habitat Assessment
Short-hand sampling
Nest location
•
•
•
•
•
Measured 2m in each direction
Vegetation type and structure
Ground water availability
Nest height and aspect
1777 individual samples with
over 26,665 possible datapoints
for 37 nests.
Questions, revisited
• Does the environment surrounding
the nest affect fledging success?
• Does it affect individual nestling
condition?
Nestlings waiting for lunch
Results
Principal Component Analysis
• Four main components in
nest microhabitat
• PCA reduces variables to a
few key factors
• Components inferred from
correlations among variables
(e.g. height & density)
• Relationships between
vegetation were also
common: More Lodgepole
Pine means less Yellow
Willow
No significant effect of vegetation on fledging success
p=0.40
p=0.97
p=0.93
p=0.70
Results, cont.
Nestlings raised in tall vegetation are lower condition
Results, cont.
Nestling condition improves as season goes on
(June 14)
(July 14)
Results, cont.
Nest vegetation height causes decrease in condition
regardless of date
p=.03
Discussion
• No effect of nest habitat on fledging success.
• Nests habitat is a poor predictor of fledging success.
• Sparrows on the ground and in willows or pines are equally
likely to experience abandonment or predation.
•This data supports the idea that predation is random.
Discussion
• Nests built in tall vegetation have lowercondition nestlings.
• Difficult for parents to get into nests?
• Foraging occurs away from tall vegetation, leading to less
provisioning?
• More time spent guarding or thermoregulating?
• Nestling condition increases with date.
• Food availability (bugs & open ground) increases over
breeding season.
• Indicates trade-off between early mating and nestling
condition.
Ending Thoughts
• Mountain White-crowned Sparrows offer a unique opportunity to
explore the consequences of nest ecology.
• Understanding ecology will help explain life-history, behavior, and
physiology.
• Future directions include looking at generational effects on
nesting behavior and ecology at other nesting sites.
Acknowledgements & Questions
Questions?
Ondi Crino
Creagh Breuner
The Breuner Lab
Doug Emlen
Bill Holben
Paul Alaback
Art Woods
Tom Bassett
Jen Smith
Bret Tobalske
Univ. of Montana MILES Program
HHMI
US FWS