Proventriculus

The proventriculus is a standard part of avian anatomy, and is a rod shaped organ, located between the esophagus and the gizzard of most birds.

[2] It is generally a glandular part of the stomach that may store and/or commence digestion of food before it progresses to the gizzard.

Hormones such as gastrin, bombesin, avian pancreatic polypeptide, and cholecystokinin affect the amount and concentration of the secretions by preventing or stimulating their release.

[7] In petrels, the proventriculus is much larger and the mucus secretions are arranged into longitudinal ridges, which creates more surface area and more concentrated cells.

These secrete a stomach oil, which is common in birds; it usually consists of undigested fatty acids, but can vary depending on the diet.

Animals with lower androgen levels have less frequent and weaker contractions, which leads to less effective digestion of food.

In general, Hymenoptera contain sphincter muscles that add pressure on the digestive components and help pass the food into the midgut.

[11] In bees, it not only controls the movement of food, but also helps separate nectar that will later be converted to honey, from pollen that will be digested.

Since it seems to be a sex specific condition, some theories are: changes in the gut biome due to diet or sex-specific pathogens, variability compared to females, or differences in behavior that could affect their exposure to biological threats and toxins [13]