Study: Cat Predation a Bigger Problem Than We Thought

Will Keightley

A new study found that estimates of cat predation on wild birds and mammals are two to four times higher than previously thought. According to the study, cats cause higher mortality to these wildlife than other anthropogenic threats such as automobile strikes, pesticides and poisons, and collisions with skyscrapers and wind turbines. 

Read the full article in The New York Times

Bird Brains

The next time you are rushing around your house looking for your car keys, you might think about the chickadees at your bird feeders. Each fall Black-capped Chickadees grow new brain cells that may help them remember the locations of things. Songbirds, like the chickadee, are the first vertebrates known to exhibit brain growth as adults. 

Because chickadees are so small, it takes a lot of food during the winter to stay warm and alive. A chickadee weighs about the same as two quarters and will easily fit on the palm of your hand. Chickadees have a high surface-area to volume ratio which means that heat loss through radiation during the cold winter can be acute. Combine this with the short daylight hours in which to forage and food for energy can be a problem. 

Chickadees prepare for the onslaught of winter by storing food. Watch them at your feeders in the fall and you will notice that they eat some of the seed, but they also carry away one seed at a time, trip after trip. They stuff the seeds in the cracks of tree bark or even in little holes and cracks on your house. I have often found a few seeds crammed into little holes when painting my house. 

Chickadees store thousands of food items a year. Each cache site is usually used only one time. One study found that they could find a cache up to 28 days later. How do they find these sites when they need them most? Songbirds have a very poor sense of smell, so they are not tracking the seed down like a dog. 

Experiments have shown that they use a complex hierarchy of visual and spatial clues to return to each cache site. Chickadees search for caches in places suggested by large landmarks such as the arrangement of trees or buildings, then they cue on local items such as a certain tree, then by things right around the cache site such as a patch of lichen on tree bark. 

In 1994 Dr. David Brodbeck, at the time a student at the University of Toronto and now a professor at Memorial University of Newfoundland, set up an array of four feeders in an aviary. They were all differently colored and in random locations. One of the feeders was baited with a peanut shoved into a little hole. The bird was placed in the aviary and it would quickly find the peanut. It was allowed to eat for 30 seconds and then it was removed from the aviary to its home cage for five minutes. 

“After 4 minutes of reading the sports section I would go into the aviary and cover up the holes on each feeder with little velcro circles”, says Brodbeck. “The bird was let back in and had to find the baited feeder and remove the velcro and eat.” 

“They were pretty darn good at this, getting around 80 percent correct in their first look,” said Brodbeck. The chickadees’ first choice was to the spatial location in the aviary, the second choice was to the position in the feeder array (second from the left for example) and the third was to the color. 

“Spatial cues are more stable than say color, and chickadees need to remember where their food is in the morning when they get up, or they die, simple as that”, said Brodbeck. “So they seem to have some sort of specialized memory system.” 

How do they remember all the cache locations and the cues to get to them with a brain that would fit on a quarter dollar? They grow brain cells. The hippocampus region of their brain expands in volume approximately 30 percent each fall from the addition of new nerve cells. This region of the brain is an important area for making new memories, especially spatial memories. Chickadees with lesions of the hippocampus continue to cache food and search for cache sites, but they are unable to find them. 

The addition of new cells and the size of the hippocampus fluctuate seasonally in chickadees, with the peak in the fall during the food cache season and is the least during the summer when food caches are not necessary. It is probably energetically costly to maintain those brain cells, so when they don’t need them in the summer, they don’t replace them.
Many of the degenerative brain diseases in humans involve the hippocampus. For example, the hippocampus in Alzheimer’s patients shrinks. Perhaps ongoing studies that are seeking a deeper understanding of songbird hippocampus regeneration will someday lead to applications in humans. 

It turns out that you aren’t a bird brain after all for losing your keys once again. You’re actually a squirrel brain. They store a lot of nuts, but apparently don’t have the trick of growing their brains each year.

Long Live the Queen

Bombus ternarius queen foraging in spring.

Each year in the bumblebee kingdom, only a juvenile queen will carry the colony’s torch through winter to produce the next generation. Everyone else – workers, drones, and the elderly queens – dies with the onset of fall frost.

Not so with the European Honey Bee, with which more people are familiar. In the dead of winter, I have often visited the honeybee observation hive at the Montshire Museum of Science, which is made with a pane of glass on each side of a thin box. The workers are all gathered around the queen in one spot. If you put your hand on the glass away from them, the glass is frigid, but the glass right in the center of the cluster is incredibly warm. Eating stored honey keeps their metabolisms high enough to produce excess heat and keep the queen warm and alive.

Bumblebees take a completely different approach. They do not put all of their energy into food storage for the winter but hedge their bet on the survival of a few queens. During the waning days of late summer and early fall, larvae begin to develop into virgin queens and males rather than the workers that have been hatching all summer. Colonies may produce up to one hundred reproductive bumblebees, hoping that at least one or two queens will survive to re-establish a colony the next spring.

When male bumblebees emerge from the cocoon, they may spend several days in the hive and drink some of the stored honey. (Bumblebees do produce some honey, just not the great quantities of their honey bee brethren.) Then the males leave the nest to forage and live on their own, often finding shelter under plant leaves and flowers during inclement weather and at night. I have seen them in the cool morning air sitting on goldenrod flower heads barely able to move. The male bumblebees have one charge in life: stay alive long enough to mate. Each male leaves a chemical attractant along a regular flight path in its territory.

New queens emerge from the hive a week after the males. Unlike the males, they will leave the nest to forage by day and return for shelter at night. And unlike their sisters, the workers, they do not add any provisions to the nest.

As the days grow shorter, a fertilized queen visits flower after flower, drinking lots of nectar to build body fat and fill her honey stomach. The honey stomach is a small sack that can hold between five-hundredths and two-tenths of a milliliter (A teaspoon holds about five milliliters). Each flower may yield only one thousandth of a milliliter of nectar, causing the queen to visit up to 200 flowers to get her fill.

Not all flowers are alike. Fall flowers like goldenrod and aster, for example, generally yield far less food than jewelweed blossoms. Bumblebees must sustain thoracic temperature at 86 to 95 degrees F. to be able to fly. So when the morning temperatures are cool, it does not pay for them to visit flowers of poor quality, because they burn as much fuel as they gain from foraging. Queens won’t emerge to forage in the cool mornings until the air temperature is around 50 degrees.

While the young queens are buzzing around foraging, they are also picking up any perfume left by a male. If the scent is to their liking, they may land and wait for the male. Mating can last up to an hour and a half, but sperm transfer generally occurs in the first two minutes. Why the long encounter? Males want to make sure the future colony belongs to them. When he is done mating he exudes a gummy substance onto the queen that blocks any other males from mating with her.

When the queen has mated, she searches for a good place to burrow into the soil for the long winter wait. Once under ground, usually one to six inches down, the queen somehow knows to avoid the false start of the January thaw and wait until late April or early May, when the warmth of the spring sun penetrates her underground home and she emerges to forage and start a new colony. Long live the queen!

Backyard Chipmunks Living the Good Life

Each fall day he appeared with a skinny face and left with ballooned cheeks. Over and over, he filled his cheeks and ran away to empty them. Our Eastern Chipmunk, it seems, is living in a good neighborhood. Our bird feeders provide him with an endless supply of sunflower seeds.

Impossible to count as he gathers them, the seeds make me wonder how many he carries on each trip. University of Vermont biology professor Bernd Heinrich pondered the same question. While examining a road-killed specimen, he found that he could stuff 60 sunflower seeds in one cheek, about a heaping tablespoon.

Chipmunks can hoard up to 8 pounds of seeds for the winter. So how many trips would the chipmunk have to take to fill up his storehouse? I weighed 120 sunflower seeds on a kitchen scale. At 2 ounces a mouthful, it would take him just 64 trips.

Sometime in November, I noticed that our resident chipmunk was no longer making trips to the seed market. And now standing on frozen ground and a bit of snow, I imagine him lying curled asleep in his nesting chamber. The main tunnel is perhaps 20 to 30 feet long with several full granaries, sleeping quarters, and separate escape tunnels. But what is it actually doing down there in the dark for five months?

Eastern chipmunks are restless hibernators. They don’t just sleep away the winter months. Chipmunks live off their seed hoard. Unlike other mammals such as bats, chipmunks don’t lay on fat for winter. Instead, they rely on good food stored in the pantry. All winter long, chipmunks eat and chill out, eat and chill out. And not just “chill out” in the sense of kicking back. They really do chill out by falling into torpor for stretches of up to eight days. Torpor is characterized by reduced body temperature, oxygen consumption, heart rate, and breathing, which all lead to much lower energy use. It makes a mouthful of sunflower seeds go a long way.

Many animals enter torpor during times of resource scarcity. When things get tough, they shut the system down and wait for better times. But torpor can have serious physiological costs. It’s not easy on the body in the long run, but it does allow for short-term survival. Individuals that have good energy reserves may not enter torpor as much as those that may need to stretch their food stores a bit more.

Each arousal from torpor is also energetically costly. Arousals can account for 80 to 90 percent of total energy expenditure each winter. But they can’t be avoided: long bouts of torpor can depress the immune system, cause dehydration, memory loss, and damage to tissues through oxidation. As an animal cools down, the circulation of antioxidant enzymes and vitamins are slowed, resulting in oxidative damage to tissues over time.

Daniel Monroe and his colleagues from Sherbrook University in Quebec thought that chipmunks might be faced with a cost/benefit trade-off. They can benefit in the short-term by going into deep and prolonged torpor to allow for energy savings in lean times, but they risk long-term physiological damage to their bodies from staying in torpor for too long if conditions stay rough.

They set out to test this with free-ranging, wild chipmunks using miniature data loggers that measured skin temperature mounted on tiny collars that the chipmunks wore around their necks, a proxy for internal body temperature. Chipmunks in the summer had skin temperatures that averaged about 99 degrees F. In midwinter, they averaged 97 degrees F when not in torpor, in a chamber that was usually below 50 degrees F. Those on a natural diet spent a total of 104 days in torpor with an average skin temperature of just 48 degrees F, while those fed on a diet of black sunflower seeds and peanuts only spent 13 days in torpor with a skin temperature of 72 degrees F. Clear evidence that chipmunks could adjust the depth and duration of torpor according to the size and composition of their food cache.

They also found that male chipmunks are more responsive than females to food supplementation. Males probably use more food during the winter to ensure that they have maximum reproductive capacity for early spring mating. Females, meanwhile, maintain deeper, more prolonged torpor to conserve their food cache for pregnancy and lactation during the early spring before fresh food is available.

The chipmunk in my backyard feeding on sunflower seeds has a diet far higher in fatty acids than those in the woods eating acorns and beechnuts. And because nut crops wax and wane over the years, woodland chipmunks may also have a smaller hoard most years. My backyard chipmunk is guaranteed a steady supply of sunflower seeds that contain 30 to 50 percent fat. With the pile of seeds that our backyard friend has, he’s surely living the good life right now, underground.

Butterflies in Winter

Mourning Cloak sunning after a long winter nap.

At 5 degrees below zero, butterflies were the last things on my mind as I brushed the fluffy snow from the porch. But as I swept away the last flakes along the railing, I noticed a small, brown sack about the size of a tootsie roll attached to the wood. It was firmly held in place by fine threads. Back inside with a warm cup of cider and my field guide, I identified it as a chrysalis of a Black Swallowtail butterfly. Many Black Swallowtail caterpillars fed on my dill plants in the nearby garden for most of the late summer. Could this be one of them? Incredibly, this chrysalis will remain in place until spring returns signaling the butterfly to emerge from its winter home and fly away. 

All butterflies develop from egg to larva (caterpillar) to pupa (chrysalis), and finally to the winged adult, which we see fluttering around. Each species has evolved a strategy that allows them to successfully pass the winter in one of these four life stages. For example, swallowtails pass the winter in the pupae stage like the Black Swallowtail I found. Skippers, quick little butterflies whose identification can challenge even avid butterfly enthusiasts, spend the winter as a caterpillar. The beautiful little coppers and blues remain as eggs through the winter. Monarchs glide to more hospitable temperatures in the south. And some, like the Mourning Cloak, hunker down and spend the winter as an adult! 

Most temperate-zone butterflies survive the deep snows and frigid temperatures of New England in a stage called winter diapause. Metabolic and respiratory rates are low and slow during diapause. The cold itself is not a direct hazard to the butterflies. However, the formation of ice crystals in body tissue is quickly lethal. To keep from freezing, butterflies reduce the amount of water in their blood (White Admiral caterpillars reduce the amount of water in their body by 30 percent) and thickened it with glycerol, sorbitol or other antifreeze agents. These chemicals function much like the antifreeze we pour into our car radiators. Mourning Cloaks can withstand temperatures down to minus eighty degrees. But it takes cold weather to trigger them to produce these antifreeze agents. If you put a Mourning Cloak in the freezer on a warm summer day, it will quickly die because it lacks any antifreeze. 

Some species of butterflies produce several generations each summer with the last generation of the summer entering diapause for the winter. The number of daylight hours, and to a lesser extent temperature, controls onset of diapause. When the summer or fall days reach a certain daylight length, the individual is genetically programmed to begin diapause at a certain time later in the season, either in its current stage or a later stage of its life cycle. Because on any given day of spring or summer there are more hours of sunlight in the northern latitudes than in the more southern areas, butterflies go into diapause earlier the farther north an individual is located to avoid the earlier onset of winter. Viceroy larvae are programmed to enter diapause after the individual receives less than 13 hours of daylight in Maryland, 13.5 hours of daylight in Vermont, and 15 hours in Newfoundland. 

Overwintering eggs employ two strategies. Eggs are either laid on the twigs of host plants, where they remain until new leaves develop in the spring and the larvae emerge and feed, or the eggs are laid on the leaf litter at the base of the plant (predominantly leafy plants that are destroyed by frost), where they remain until the plant sprouts from the ground in the spring. The main difference between the two is host plant type. Species which feed on herbs place their eggs on the ground and species that feed on trees or shrubs place them on the woody portions. Some, like the endangered Karner Blue, rely on an insulating blanket of snow to protect them from harsher weather. When there is little snow, eggs can become damaged by dry, cold air. 
 

Adults that overwinter, such as the Mourning Cloak or the Milbert’s Tortoiseshell, store fat in there bodies in the fall. Before entering diapause they find a place to hide, such as hollow trees or logs, cracks in rocks, or inside old buildings. In these protected and somewhat insulated hideouts, they enter diapause until the longer and warmer days of spring bring them forth to mate and lay eggs for the next generation. These early spring adults may have wings that are very tattered and ragged from their relatively long life of 8 to 10 months. 

To break diapause in the spring an individual must pass through a long period of cold weather and into a longer daylight period. The cold period must be months long to trigger the end of diapause. If it were shorter the individual might end diapause during a short warm spell only to be clobbered by the next arctic front.
The beautiful butterflies are still around us, despite the snow. Their special adaptations will allow them to emerge during the warm days of spring. I’ll be watching the little Black Swallowtail chrysalis on my porch throughout the winter and the day it bursts from its case and spreads its wings, I’ll know it is truly time to put the snow shovel away and sharpen the garden spade.

Record Breaking Early Flowering in the Eastern U.S.

Using the meticulous phenological records of two iconic American naturalists, Henry David Thoreau and Aldo Leopold, scientists have demonstrated that native plants in the eastern United States are flowering as much as a month earlier in response to a warming climate.

The new study is important because it gives scientists a peek inside the black box of ecological change. The work may also help predict effects on important agricultural crops, which depend on flowering to produce fruit. The study was published online today (Jan. 16, 2013) in the Public Library of Science One (PLoS One) by a team of researchers from Boston and Harvard Universities and the University of Wisconsin-Madison.

Compared to the timing of spring flowering in Thoreau's day, native plants such as serviceberry and nodding trillium are blooming 11 days earlier, on average, in the area around Concord, Mass., where Thoreau famously lived and worked. Nearly a thousand miles away in Wisconsin, where Leopold gathered his records of blooming plants like wild geranium and marsh marigold, the change is even more striking. In 2012, the warmest spring on record for Wisconsin, plants bloomed on average nearly a month earlier than they did just 67 years earlier when Leopold made his last entry.

Read more from University Wisconsin-Madison...

Tallying Birds County by County: Results of the Vermont County Bird Quest 2012

Location of 2012 eBird checklists in Vermont

From the drop of the ball on January 1 to the last owl hoot on December 31, hundreds of birders scoured fields and fens, mountains and meadows, lakes and lawns to discover as many species as possible during a single calendar year. The second annual Vermont County Birding Quest pitted county versus county, birder against birder — all engaged in a friendly rivalry for top honors of the highest species count. The main idea behind the year-long Quest was simply to get people out birding, promote camaraderie, and better document bird life across the state, using Vermont eBird. With over 28,000 eBird checklists submitted and nearly 2.3 million birds tallied, there is no doubt it was a huge success!

Green Mountain Birders Put Up Big Numbers


The final results were based on a carefully calculated "par" system, realizing that not all Vermont counties are created equal in terms of avian diversity. Par scores reflect the number of species that a given county should find in a year with consistent birding effort. Although Chittenden took top 2012 honors in absolute numbers of species tallied with 242, Washington County won the 2012 Quest Cup, 25.5 over par and just shy of the 200 bird mark, a remarkable effort for a county with few large water bodies. Top checklist honors goes to Windsor County with 4,937 checklists submitted to Vermont eBird.

Many birders ventured outside their home counties, and the statewide leaders in total species observed were Jim Mead (252), Ian Worley (242), and Allison Wagner (240). Ian Worley submitted a remarkable 1,721 eBird checklists, while Craig Provost with 1,394 and Jim Mead with 1,196 took home very respectable silver and bronze in this category. Birders who identified 150 species or more in a county were also inducted into the prestigious "150 Club".

Congratulations to everyone for a fun year of birding. We hope some of you will vie for top honors in 2013! If ever you don't, all of the data collected in Vermont eBird is valuable for science, education and conservation.

Awards

County Team Awards

The County Cup
Presented to the county with the highest number of species found under the par system mentioned above. The winner will keep and display the cup until the next winner is announced after the following year.
County Species List
Awarded to the county with the highest raw total of species found.
County Checklist Award
Given to the county that submits the most checklists to Vermont eBird in a calendar year.

Individual Awards

The Vermont eBird 150 Club
Awarded to each Vermont eBirder that has 150 or more bird species in a county reported to Vermont eBird in a single calendar year. Finish one or go for all 14 counties!
County Bird Champs
Given to the birder with the highest species count for each county. No par or weighting necessary for this one!
County Checklist Champs
Awarded to the birder with the most eBird checklists for each county.
State Bird Champ
The individual with the highest number of species found in the state during the year.
State Checklists Champ
Awarded to the birder that enters the most eBird checklists in the state.

Dragons and Damsels of New Hampshire Lecture

Please join the Mascoma Chapter of New Hampshire Audubon and VCE this coming Monday, January 14 at 7:00 PM in the Mayer Room of Hanover's Howe Library for a co-sponsored talk by NH Audubon's noted dragonfly expert Pamela Hunt.  Pam's talk, "Dragons and Damsels of New Hampshire" is free and open to the public.  It promises to be both engaging and informative.

Pam's program will provide an overview of the biology and ecology of dragonflies and damselflies, highlighting some of NH's more notable species. It also will include results of the “NH Dragonfly Survey,” a five-year citizen science project coordinated by Pam, that documented the distribution of these eye-catching but relatively little-known insects across the state.

Pam, a long-time VCE colleague, began birding 30 years ago, inspired by a pre-teen visit with her uncle to Brigantine National Wildlife Refuge in NJ. Today, she is NH Audubon’s Avian Conservation Biologist and NH Fish and Game's State Ornithologist, focusing on bird research and monitoring in the state. Most recently she authored NH's "State of the Birds" report. In addition to working on statewide bird conservation issues, Pam also studies Whip-poor-will biology and ecology.

VCE's Sara Zahendra will be on hand to very briefly present an overview of our Migratory Dragonfly Connectivity Project.  She hopes to see many of you there!

 

Visit the Mascoma Audubon website for future talks, including one by our own Kent McFarland.