Stability of pigeon body weight under free-feeding conditions.

The team watched adult male pigeons eat all they wanted for 30 days.

They weighed each bird every day to see if the weight stayed steady.

The goal was to learn how long you must wait before the weight becomes a true baseline.

The birds held the same weight day after day.

After only seven days the number stopped moving, so longer waits were not needed.

Bachman et al. (1988) saw pigeons lose weight and cool their bodies at night when they had to work harder for food.

That study shows weight can drop fast when food costs effort; Gadow et al. (2006) shows weight sits still when food is free.

Green et al. (1987) gave birds both free and earned food; the birds ate less total food and worked less.

Together the three papers draw a clear line: free food keeps weight steady, mixed or costly food makes it fall.

If you run animal labs, you now know one week of free feeding is enough to set a safe weight baseline.

This saves time and keeps birds healthy, letting you start the real experiment sooner.

A free-feeding weight is the stable body weight an animal maintains with continuous, unrestricted access to food. In operant research with pigeons, it is the baseline used to set humane food-deprivation levels for reinforcement.

Before this study there were no formal guidelines for how long to hold pigeons on free access before treating their weight as a stable baseline.

Pigeons were weighed on arrival, held in quarantine with free food access for seven days, and then weighed daily for 30 more days with food still available. Male pigeon weights showed no significant change over that period.

That means seven days of free access is enough to establish a baseline weight in adult male pigeons. Female pigeons showed higher day-to-day variability, which the authors note might even help distinguish sexes.