Ewertetal. • DISTRIBUTION OF 
MIGRANT LANDBIRDS ALONG LAKE HURON 543 
habitats. However, fall migrants were more 
evenly distributed with respect to distance from 
the shoreline than spring migrants, perhaps 
because of both a relative absence of midges 
and abundance of widely distributed phytopha¬ 
gous insects during the peak migration period of 
late August and early September. Midges were 
significantly less abundant within shoreline hab¬ 
itats in fall compared to spring, resulting in a 
reduced shoreline/inland contrast in midge abun¬ 
dance Seefelt (1997) noted migrants feeding on 
Lepidoptera larvae and adults, Coleoptera. Ho- 
raoptera, and other taxa both at the shoreline and 
inland during fall migration, when leaves appear 
to support a diverse arthropod fauna. Our results 
suggest midges do not have a prominent role in 
affecting migrant distribution during fall and that 
overall food supply is more evenly distributed in 
fall than spring. 
The importance of prey produced from terres¬ 
trial or aquatic sources to birds varies spatially, 
temporally, and by bird species (Murakami and 
Nakano 2001, Nakano and Murakami 2001). 
Midge productivity varies dramatically within a 
lake and regionally (Tokeshi 1995) due to larval 
food supply (Berg 1995) and other factors such as 
bottom sediment characteristics (e.g., sand, bed¬ 
rock, cobble, silt), water quality (Armitage et al. 
1995), and water depth (Berg 1995). Chironomids 
are common in many aquatic ecosystems (Pinder 
1986. Benke 1998) and are prey for passerines in 
other landscapes (e.g., Murakami and Nakano 
-002). Studies suggest that other Great l^akes 
shorelines, including those with sandy substrates 
°pen io high wave action may support smaller 
numbers of spring migrants, perhaps because 
these shorelines have fewer aquatic insects than 
nearby wetlands, 0.5-1.2 km from the shoreline 
'Hyde 1998, Hazzard 2001). Only sites with 
appropriate nearshore bathymetry, near shore 
substrate, near shore terrestrial plant communities. 
perhaps other conditions, may provide the 
food supply and foraging substrates preferred by 
migrant species that exploit aquatic emergent 
insects such as midges. 
The relative importance of aquatic dependent 
arthropods to migrants may vary latitudinally with 
leather and climate change. Migrants, especially 
ear ly season insectivorous migrants or those al 
more northern latitudes, are most likely to arrive 
before leaf-out in spring (Slagsvold 1976) and be 
more dependent on aquatic insects compared to 
late arriving migrants or migrants at more 
southern latitudes, such as central Illinois where 
migrants fed primarily on geometrid caterpillars 
(Gruber and Graber 1983). The importance of 
shoreline habitats to migrants may also be 
affected by timing of midge or other arthropod 
emergence related to weather or climate changes 
that modify synchrony between prey abundance 
and timing of migration (Strode 2003). 
Identifying attributes of important stopover 
sites and then ranking stopover sites for conser¬ 
vation purposes is challenging (Hutto 2000) but in 
progress (Stralberg et al. 2011). Coastal areas, 
including the Great Lakes, may he important areas 
for conservation efforts (Petit 2000) given the 
high concentrations of birds found along many 
shorelines and increasing development pressures 
that threaten these areas (Simons et al. 2000). 
Identifying and protecting sites where birds can 
safely and rapidly replenish resources may be 
critical to maximizing their survival and repro¬ 
ductive success (Moore et al. 1995). Protection of 
vegetated shorelines, especially those bordered by 
productive nearshore aquatic communities should 
benefit migrants both in the Great Lakes region 
and perhaps elsewhere, including sites at compa¬ 
rable latitudes in the northern USA and Canada. 
Similar ecological relationships at wetlands (e.g., 
Sealy 1988), streams (Wilson 2001). and inland 
lakes may also support many migrants and be 
disproportionately important to migrant landbirds. 
ACKNOW LEDGMENTS 
We are grateful for financial support from the National 
Fish und Wildlife Foundation, R. E. Olds Ransom Fidelity 
Company. Central Michigan University, The Nature 
Conservancy, and Dr. and Mrs. Lewis Batts. We thank 
Dr. and Mrs. P. M. Pittman for in-kind support. * • L. 
Hudson and O. A. Saelher kindly identified midge species. 
We arc appreciative of the efforts ol N, E. Seefelt for 
participating in data collection, data entry and offering 
insightful suggestions to improve design and implementa¬ 
tion of the study. C. E. Braun and 2 anonymous reviewers 
improved the manuscript. We thank Hiawatha National 
Forest. Lake Superior Stute Forest, and Marilyn Twining 
for permission to conduct the study on their land. 
LITERATURE CITED 
Albert. D. A.. S. R. Denton. B. V. Barnes, and K. E. 
Simpson. 1986. Regional landscape ecosystems of 
Michigan. School of Natural Resources. University of 
Michigan, Ann Arbor, USA. 
ALERSTAM. T. .and A. LindstrOm. 1990. Optimal bird 
migration: the relative importance of time, energy and 
safety. Pages 331-351 in Bird migration: physiology 
