Impacts of vegetative manipulations on common tern nest success at Lime Island, Michigan

  • Published source details Cook-Haley B.S. & Millenbah K.F. (2002) Impacts of vegetative manipulations on common tern nest success at Lime Island, Michigan. Journal of Field Ornithology, 73, 174-179.


This study investigated the effects of herbicide treatment on vegetation structure plus nest-site selection and nesting success of common terns Sterna hirundo at a breeding colony on an old coal dock (colonised by grasses and forbs) on Lime Island (46°05'N, 84°01'W) in the Saint Mary's River, Michigan, northern USA.


In 1998, more than two weeks before the arrival of terns, vegetation manipulations were carried out in a 25 × 50 m area of the nesting colony. The experimental area was divided into 5 × 5 m plots, which were randomly allocated to one of three treatments: all vegetation sprayed with herbicide ('fully sprayed'; n = 16 plots); any vegetation over 1 m in height, or likely to exceed 1 m during the growing season, sprayed with herbicide ('partially sprayed'; n = 17); or left untreated (n = 17). The herbicide used was Round-Up® (120 ml/3.6 l water).

Nests were subsequently checked every 2–3 days from May to August to monitor clutch size, hatching success and the fate of eggs.



Not all plots were used by nesting terns, but 131 nests were initiated in nine fully sprayed plots (average: 14.6 nests/used plot), 47 nests in seven blocks partially sprayed plots (6.7 nests/plot), and 50 nests in 11 control plots (4.5 nests/plot). Average clutch size did not differ significantly among the three plot types. Fully sprayed plots had significantly lower standing vegetation cover (24% versus 41%) and higher litter cover (68% versus 52%) than partially sprayed plots.
Nest success was affected by treatment type, with the proportion of nests that were successful (i.e. hatched at least one egg) highest in partially sprayed plots (72%), intermediate in untreated plots (64%) and lowest in fully sprayed plots (37%).
Hence, despite their apparent preference for areas with low standing vegetation cover (i.e. fully sprayed plots) when selecting nest sites, terns had highest nesting success in areas with moderate amounts (40–50%) of standing vegetation cover.

Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at:


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