Feeding latency

Feeding latency is the elapsed time from a defined starting event to a defined feeding event. An experiment might measure from food presentation to an individual's first peck or to the first bird feeding in a social group. Those endpoints answer different questions. The start, the feeding criterion and the observation limit must all be specified.

In an original example, an animal feeds after $20\mathrm{s}$ without a novel object and $80\mathrm{s}$ with one nearby: the novelty-associated increase is $60\mathrm{s}$. Another changes from $100$ to $130\mathrm{s}$, an increase of $30\mathrm{s}$. Comparing only the two novel-condition times reverses the ordering obtained by comparing their changes.

A group-level first-feeding time is $T_{\mathrm{group}}=\min (T_1,\dots ,T_n)$, if $T_i$ denotes each member's time under that same group trial. This identity requires no independence assumption. It also shows why a group endpoint cannot be treated as though it were a measurement of every member: one early feeder determines the recorded minimum.

If recording ends after $180\mathrm{s}$ before feeding occurs, the observation is subject to right censoring: the time exceeds the recorded limit. Replacing it by an observed time of exactly $180\mathrm{s}$, or by infinity, changes what was measured.

A finch study combined whether groups fed at all with feeding latency comparisons in familiar and novel-object conditions. Keeping those outcomes separate preserves information that an average of observed feeding times alone could lose.^[ref]