Foraging time and dietary intake by breeding Ross's and lesser snow geese / Mark L. Gloutney, Ray T. Alisauskas, Alan D. Afton, and Stuart M. Slattery.

Includes bibliographical references (pages 85-86).

We compared foraging times of female Ross's
(Chen rossii) and Lesser Snow Geese (Chen caerulescens
caerulescens) breeding at Karrak Lake, NT, Canada
and examined variation due to time of day and reproductive
stage. We subsequently collected female geese that
had foraged for known duration and we estimated mass
of foods consumed during foraging bouts. Female Ross's
Geese spent more time foraging (mean % ? SE = 28.4
? 1.3%; ? = 0.0002), on average, than did female Lesser
Snow Geese (21.5 ? 1.4%). Foraging time by female
geese differed among reproductive stages, but differences
were not consistent among time periods (stage-bytime
block interaction, P=0.0003). Females spent considerably
more time foraging during prelaying and laying
than during incubation. Ross's Geese also spent a greater
percent of time feeding (83.0?2.8%) during incubation
recesses than did Lesser Snow Geese (60.9?3.6%). Consumption
of organic matter during foraging bouts was
minimal; estimated consumption averaged 9.6?4.0 and
12.4?4.6 g (mean ? SE) dry mass/day before incubation
and 5.9?2.0 and 5.7?2.1 g dry mass/day during incubation
for Lesser Snow and Ross's Geese, respectively.
Diets consisted primarily of mosses (bryophytes),
Chickweed (Stellaria spp.) and Sedges (Carex spp.). Before
incubation, eggshell consumption was estimated as
4.3?3.2 and 0.4?0.3 g dry mass/day for Lesser Snow and
Ross's Geese, respectively; neither species consumed
eggshell during incubation. We conclude that eggshell
from nests of previous years is likely an important
source of dietary calcium used to meet mineral demands
of eggshell formation at Karrak Lake. Our findings of
wide disparities between foraging time and food intake
indicate that results from studies that do not directly
measure intake rates remain equivocal. Finally, we propose
four hypotheses accounting for foraging effort that
evidently yields little nutritional or energetic benefit to
geese nesting at Karrak Lake.