Tag Archives: bird biology

Fall is Social Season for Blue Jays

Posted on October 15, 2019 by kkeohane

Fall holidays mean family gatherings – for people and for Blue Jays. Much like people, these highly social birds are more active in the fall, when the harvest is good and families are reuniting. This pattern is borne out by data on eBird, when observers’ Autumn checklists show a spike in sightings. Here are a few explanations for jays’ noisy behavior right now. 

Image: David Young

Predators on the move mean agitated birds 

When there is a predator nearby, many birds exhibit mobbing behavior to warn others of the threat. This means loud calling and erratic flight patterns. During migration, higher numbers of hawks, owls, and falcons may excite young jays and cause them to vocalize more frequently.  

Blue Jays have also been known to imitate hawk calls. Some researchers think this is a signal to their flock of a potential threat nearby. Others believe Blue Jays are cleverly trying to scare other birds away from their food source. Ross D. James, in a 2002 edition of Ontario Birds, theorizes that young birds learn raptor calls during periods of high stress and excitement and therefore will reproduce them under those same conditions.  

Acorns are plentiful  

Image: Peter Flood 

Every two to five years, Oak trees drop their acorns in much higher abundance than usual. These periods of higher acorn production are called “mast years” and greater Boston residents have taken notice. Fortunately for Blue Jays, who eat mostly seeds, this means lots and lots of food. They flock to areas with high densities of Oak trees, like many Massachusetts forests, and call out to their kin that they’ve hit the jackpot. 

Winter flocks are recruiting 

Blue Jays are winter residents in Massachusetts. Some individuals do migrate, but little is known about how or why they decide to do so. Families group together in large flocks starting in the fall. These flocks are constantly communicating potential threats and food sources since fledglings are still learning the ropes.  

One study of Blue Jays at Mass Audubon’s Wachusett Meadow Wildlife Sanctuary observed wintering jay groups of 14-49 individuals. These birds tended to stay in the same groups throughout the winter and in subsequent years.  

Image: Raina Aiello 

Have you noticed more Blue Jay activity lately? Let us know in the comments! 

How Do Pelagic Birds Find Fresh Water At Sea?

Posted on August 31, 2018 by William Freedberg

The short answer: they don’t.

Seabirds drink ocean water, and excrete the excess salt that would otherwise leave them dehydrated. Specialized glands, located above the beak and just under the eyes, filter salt ions from seabirds’ bloodstream. The glands also draw out just enough water to dissolve salt into a highly concentrated saline solution, which runs out through the bird’s nostrils.

If you’ve ever seen a gull standing on dry land, with fluid dripping down the tip of its beak… that’s because it’s expelling salt!

These glands can atrophy and stop working if not regularly used. Seabirds at zoos and wildlife rehabilitation clinics actually need to be kept in saltwater—if their glands stop pumping, the birds can experience salt poisoning when re-exposed to ocean water.

 

A Sooty Shearwater exhibits a typical “tubenose” beak structure: elongated nostrils through which salt is excreted. Photo © William Freedberg

 

Terrific Tubenoses

Birds in the family Procellariformes (which includes albatrosses, shearwaters, petrels and storm-petrels) excrete salt through one or two tubes that sit atop their beaks, giving the group the informal name of “tubenoses”. A common misconception among birders is that this tube is an organ used uniquely for excreting salt.

In fact, it’s not clear that these birds process salt any more efficiently than any other seabirds, like pelicans or marine ducks. Tubenoses’ beak structure might help them keep saline excretions from blowing into their eyes in high oceanic winds, but that’s probably not its primary function.

Recent evidence suggests that these tubes help channel airborne scents, contributing to tubenoses’ ability to sniff out plankton blooms on the open ocean. There’s also evidence that the nasal tubes of albatrosses contain pressure-sensing nerves, helping these birds find and navigate the rising air currents they use to stay aloft.

 

Seabirds Under Threat

Seabirds’ exquisitely fine-tuned sense of smell serves them poorly in oceans plagued by plastic pollution. It turns out that plastic, especially when covered in marine algae, smells just like the zooplankton seabirds love to eat.

While some seabirds that frequent Massachusetts waters are doing well (like Wilson’s Storm-Petrels and Cory’s Shearwaters) others are in serious trouble. And unlike some declining groups, pelagic birds’ absence flies largely under the radar of most land-bound naturalists. Among myriad dangers, entanglement in fishing gear, climate volatility, and invasive species drive seabird declines.

Help fight these threats by purchasing American-caught seafood—fishery regulations here favor seabirds more than in much of the world— and by reducing plastic waste.