Dropping behavior occurs at any time of year but is more prevalent in the winter during low-tide hours, most likely due to having more access to larger mussels. Kelp gulls will fly over 0.5 km to a preferred substrate on which to break their prey. Height from which the prey is dropped will increase after each drop of the prey. Once the prey is dropped, a gull will descend as quickly as possible to recover its prey. This is likely to prevent kleptoparasitism, which is very common in prey-dropping. On average, a kelp gull will descend at an average of 4 m/s in comparison to the prey’s fall of 5 m/s, which allows the gull to reach the ground about 0.5 seconds after the prey has landed onto the surface . Adult kelp gulls have a higher success rate of breaking and obtaining their prey while prey dropping than juvenile kelp gulls. Western gulls are one of the many species of gulls that have been observed to drop their prey on the ground. A study observed that a major factor influencing dropping behavior in these gulls had to do with the mass and size of the prey being dropped. When performing a study using different sizes of Washington clams, smaller clams were normally pecked at. The larger clams however were dropped unless they were too heavy to carry, usually exceeding 268 grams in weight.Drop behavior differs between adult and immature western gulls. All adult western gulls that have been studied displayed prey dropping behavior, and dropped from an average off 118 meters away from where they were originally retrieved. In the study, dropping occurred either over mudflats or a parking lot, which correlated with weight of the clams, which average clam weights were 106.7 g and 134.3 g respectively. Immature gulls meanwhile are much more clumsy with their dropping, and only 55% of juvenile western gulls that were observed displayed this behavior. Juvenile gulls also did not seem to have a correlation between the weight of the clam and the height the clam was dropped at, though it is noted that the younger gulls seemed to drop their prey at much lower heights than their older peers. This could be evident that juvenile gulls are learning this behavior through trial and error. The low height at which the clams are dropped may also result in the amount of times the younger gulls had to drop their prey. Immature western gulls tend to drop their prey more frequently than the older gulls do, most likely due to inconsistency in drop height as well as the height of the drops.Unlike most birds who drop their prey, western gulls actually seem to prefer softer substrates over larger substrates when dropping their prey, and only seem to drop their prey on hard surfaces if their prey is heavier.