Subjects and Housing Conditions:
To assay male foraging ability and acquire recordings of male songs, we
obtained 25 adult male zebra finches of unspecified age from Magnolia
Farms avian breeder (Anaheim, CA).
Birds were housed in a group cage
for four days upon arrival, then weighed with a Pesola scale and placed
in individual cages in a group room. Cages were wire and measured 48cm x
25cm x 30cm with two perches and one cuttlebone each. Food and water
were provided ad libitum. Vivarium rooms were illuminated on a 13:11
light-dark cycle. Temperature in the room was maintained at 22°C.
Housing conditions were approved by Tulane IACUC Protocol 0427R.
To measure female preference, we obtained 15 adult female zebra finches
of unspecified age, also from Magnolia Farms. Females were purchased 18
months after the male zebra finches were purchased to minimize the
possibility of prior interaction between males and females due to
overlap at Magnolia Farms. Housing conditions were identical to the
first group of birds. Males were not housed in the facility at the same
time as the females, and females were not exposed to their songs prior
to testing.
Novel foraging assay :
To solve the novel foraging task, males learned to remove lids covering
baited wells in a block. The block was 10 x 14 cm and composed of grey
composite plastic with six drilled wells (1.7 cm diameter x 1 cm depth).
The food reward consisted of 2-3 millet seeds placed in the bottom of 4
of 6 wells. Baiting patterns were randomly generated with R (R
Development Core Team 2016) and changed between each trial. Lids were
made of blue and yellow round plastic counting chips glued to a round
rubber bottom, such that lids fitted into the wells and needed to be
lifted off in order for the bird to obtain the food reward. Stages
consisted of: (1) just the block, (2) lids placed adjacent to, but not
covering baited wells, (3) lids half-covering wells, (4) lids tipped
into wells, and (5) lids completely covering and fitted into wells.
Testing was done in the housing room and birds remained in auditory
contact with their flockmates to alleviate stress caused by moving or
social isolation. Dividers were placed between cages during testing so
that neighbors of the study subject could not see the task beforehand.
Trials consisted of two-minute periods in which the block was placed in
the cage and the bird was allowed to interact with it. After each
two-minute trial the block was removed from the cage for approximately
ten minutes while other birds were tested. Each bird was given six
trials per day. Food was removed five hours before testing to increase
motivation. After each round of testing, a motivation check was done in
which a food dish was placed in the cage and the time it took the bird
to approach and eat from it was recorded. If birds ate from food dishes
in less than one minute, they were considered sufficiently motivated.
All birds passed all motivation tests, indicating that food removal left
them sufficiently motivated to obtain a food reward.
Birds had to eat from at least two baited wells to pass a trial, and had
to pass three out of four consecutive trials to move on to the next
stage. Passing criteria remained the same throughout the novel foraging
task. If birds were stuck on a particular stage for more than four days,
they were moved back to a previous stage or, for stage 1 only, the block
was left in the cage overnight. If a bird did not complete a step (not
the entire task, just one step) within 60 trials, it was removed from
trials and designated a Non-Solver, as further food removal and testing
was potentially harmful to birds and in our judgment these individuals
were not likely to progress further.