On some birds, the stomach actually shrinks in order to allow them to carry additional food on long flights. This incredible adaptation is known as "gizzard shrinkage" and is particularly common in species of birds that undertake long migratory journeys.

During migration, birds need to consume large amounts of food to fuel their journey. However, carrying excess weight can hinder their ability to fly efficiently. To combat this, some birds have evolved the ability to shrink their stomachs, allowing them to carry more food without adding unnecessary weight.

One example of a bird species that exhibits gizzard shrinkage is the bar-tailed godwit. These birds undertake one of the longest non-stop flights in the animal kingdom, flying from Alaska to New Zealand without stopping to rest or refuel. By shrinking their stomachs, bar-tailed godwits are able to carry enough food to sustain them during the arduous journey.

Other birds that exhibit gizzard shrinkage include various species of shorebirds, such as sandpipers and plovers, as well as some species of waterfowl. These birds rely on their ability to shrink their stomachs in order to survive long flights across oceans and continents.

Gizzard shrinkage is just one of the many incredible adaptations that birds have evolved to cope with the demands of migration. By understanding how birds are able to carry additional food on long flights, researchers can gain valuable insights into the physiological mechanisms that enable these incredible journeys.

For more information on gizzard shrinkage and other adaptations in migratory birds, check out the following resources:

• Audubon article on how birds adapt their guts for migration
• Science Daily study on the physiological adaptations of migratory birds

By studying the incredible adaptations of migratory birds, researchers can gain a deeper understanding of the challenges and obstacles that these birds face during their long journeys across the globe.

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