Gray Catbird will swallow the berry, not mash it.
While I enjoyed photographing a few birds at a berry buffet, I thought I picked a simple topic to share on the relationship between migratory birds and berries. I was berry wrong…again.
Many studies have a veritable berry bonanza of conflicting theories. Other studies indicate how could only one test certain parameters in a berry-eating bird if it’s only studied at the beginning of migration and not during or after. Research certainly varies on theories relating to fats versus proteins. For example, increase in body mass has been correlated to fats. And researchers did agree that certain birds switch their insect/invertebrate/seed/nut/plant diet to fruit for migratory prep. They also agree that birds overeat (hyperphagia) to consume a high energy diet to sustain their travel.
Energy can be stored as carbs, proteins, and fats. Fats can increase the body weight of birds as much as 50%. Fat storage occurs in their muscles, organs, and in pads under their skin. Those fats provide eight times more energy. Another astonishing fact is that when fat metabolizes, it releases water which helps reduce dehydration on a long trip. But other studies suggest some migrants have fat-free diets. More recent studies indicate that fat-free deposition seems to occur in larger species. However protein is needed to maintain that body mass so certain plants and insects offer a higher percentage of proteins. Recent studies now specify that significant protein storage must also happen. Finally certain studies mention the benefits of antioxidants from fruits during migration but more recent studies decline to accept them as necessary!
GULPERS
Scientists classify fruit eaters as gulpers or mashers. Gulpers swallow the whole fruit such as the Gray Catbird and the Northern Mockingbird.
Northern Mockingbird is also a gulper.
MASHERS
Mashers work the peelings and pulp with their beaks like the Great Kiskadee and the Northern Cardinal. I observed both gulpers and mashers also used their tongues. Both methods met their nutritional requirements but mashers expended more energy and also lost some pulp.
mashes the fruit and may drop part of the fruit.jpg
NATIVE PLANTS VERSUS EXOTICS
Several studies suggest when birds switch over their diet from insects, seeds, or invertebrates for migration prep, they appear to select higher quality native plants instead of non-native, nutritionally lesser berries. However when native berries are rare, birds will definitely dine on non-native fruit. I would be remiss if I didn’t mention that birds can be dispersers of exotic, highly invasive plants such as the Brazilian pepper tree.
Birds feeding on berries can be mutually beneficial for the plant and the bird. While the birds acquire the nutrition from eating the fruit, the fruit seed can be dispersed elsewhere. Certain bird digestive tracts scar the seed to enable it grow from the nitrogen-rich droppings. Other avian species actually destroy the seed which doesn’t benefit the plant. Still others merely regurgitate the seeds without going through the gut.
DO BIRDS GET DRUNK FROM FERMENTED FRUIT?
Some birds may appear intoxicated from dining on fermented fruit. Many references provide anecdotal evidence instead of field studies. Therefore some researchers infer the birds that appear uncoordinated are overweight, have eaten too much, and cannot fly for awhile. Meanwhile studies of the Cedar Waxwing illustrate alcohol poisoning does occur in this species.
CONCLUSION
I found two studies that give an overall picture of what I gleaned from my research review. One study showed that birds migrating to Central and South America seemed to benefit a high berry diet more than short distance migrants. This study analyzed blood cells, plasma, feathers, and fecal samples. Researchers found no link that antioxidants played any role. A lot of berry-eating appeared more to their high fat and carbs menu. And I’ll also add the study that included the need for protein storage for a successful migration. Therefore these implied the importance of conserving habitats with native fruiting trees and shrubs along the migratory route.
PHOTO 16 Gray Catbird dines at a berry bonanza
BERRY WELL!
SPECIES LIST:
* Recorded/documented in the Yucatán Peninsula ; all are not common so check ebird.org for frequency/updates
Photographed in the USA and Yucatán Peninsula
*Gray Catbird, Dumetella carolinensis, Maullador Gris (Spanish), Ch’ich’ miis (Mayan)
*American Robin, Turdus migratorius, Mirlo Primavera (Spanish)
Northern Mockingbird, Mius polyglottos, Centzontle Norteño (Spanish)
*Northern Cardinal, Cardinalis cardinalis, Cardenal Rojo (Spanish), Chakts’iits’ib (Mayan)
*Great Kiskadee, Pitangus sulphuratus, Luis Bienteveo (Spanish), X takay (Mayan)
For this holiday season, may there be peace, respect, and tolerance: MERRY CHRISTMAS, FELIZ NAVIDAD, HAPPY HANUKKAH, HAPPY KWANZAA, BUONE FESTE NATALIZIE, KURISUMASU OMEDETO, JOYEUX NOEL, FROEHLICHE WEIHNACHTEN, FELIZ NATAL, KRISMASI NJEMA, SAWAT DEE WAN, AND HAPPY HOLIDAYS
DISCLAIMER: Some references may not agree or I may not have found the most recent name changes. Plus autocorrect doesn’t like scientific names or language translations.
Sal a Pajarear Yucatán (Guía de aves), A Guide to the Birds of Mexico and Northern Central Mexico, The Crossley Guide,
Premigratory Hyperphagia in Birds, Eugene P. Odum, Ph.D. American Journal of Clinical Nutrition Vol 8 Sept-Oct. 1960
https://greathollow.org/wp-content/uploads/2024/02/Carter-et-al.-2024-Oecologia.pdf
https://greathollow.org/news/studying-the-importance-of-berries-to-migrating-songbirds
https://www.jstor.org/stable/10.1525/auk.2010.10068
https://www.audubon.org/news/migratory-birds-native-berries-best
https://www.audubon.org/news/what-happens-when-birds-get-drunk
https://www.allaboutbirds.org/guide/Cedar_Waxwing/overview
https://www.theguardian.com/environment/blog/2008/sep/08/wildlife.conservation
https://www.sciencedirect.com/science/article/abs/pii/0300962995020918
https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2435.14164
Cherie Pittillo, a “nature-inspired,” photographer and author, explores nature everywhere she goes. She’s identified 56 bird species in her Merida, Yucatan backyard view. Her monthly column features anecdotes about birding in Merida, Yucatan, and also wildlife beyond the Yucatan.
Contact: [email protected] All rights reserved, ©Cherie Pittillo
