Happy Holidays

Rocky Mountain National Park

Happy Holidays! A break for this week, but I'll be posting again next year!

Mistletoebird

♀ Mistletoebird, Dicaeum hirundinaceum

Named for its food preference, the Mistletoebird can be found throughout mainland Australia and parts of Papua New Guinea and eastern Indonesia. This bird is the only member of the Dicaeidae family, the flowerpeckers, found in Australia and may therefore be also referred to as the Australian Flowerpecker. The digestive system of the Mistletoebird is simple allowing berries to pass through quickly. The sticky seed is then excreted onto branches allowing the parasitic plant to spread and grow.

Cedar Waxwing

Flock of Cedar Waxwings, Bombycilla cedrorum

Cedar Waxwings are found throughout most of North America especially during the winter months. During this time, they will feast on cedar berries, mistletoe, honeysuckle, and mountain ash berries to name a few. The vast amount of fruit these birds eat can cause problems of intoxication. During the non-breeding season, the flock numbers can vary from only a handful to close to fifty individuals. These flocks communicate by means of a "flock call" and keep a compact formation when flying, perching, bathing, or feeding. The social behavior is exhibited early in life as fledglings tend to form flocks with the other young of neighboring nests.

Winter Roosting

Flock of various Grackles,  Quiscalus

The approach of cold weather results in a number of bird species to gather together in large communal flocks. Some of the more common species include the Common Grackle, American Robin, Dark-eyed Junco, Snow Goose, and sometimes even Blue Jays to name but a few. This flocking behavior is not sudden, but rather the gradual congregation of smaller groups into larger ones. This begins early fall and reaches a peak during mid-winter. There are two main explanations for flocking together: enhanced foraging success and reduced predation. With less time spent finding food and avoiding predators, foraging success can vastly increase. When in large flocks predator detection is higher, chance of death lower, and "strength in numbers" may deter predation. The behavorial dynamics of a winter flock are influenced by food availability, familiarity, and overall composition as not all flocks are composed of a single species.

Estivation

Bearded Dragon, Pogona vitticeps

Another major form of dormancy, estivation is similar to the metabolic and temporal reduction of hibernation, but used by species found in dry, hot environments. It is a state of aerobic hypometabolism where those species retreat to estivate in sheltered sites. They are active for a set period of time during the year, sometimes only a few weeks, to feed and breed. One characteristic factor of estivation is the methods of water retention both physically and metabolically. Balancing water retention could be a change of concentration in the urine, it could be the burrow construction, or it could be taking advantage of the environment to prevent dehydration.

Hibernation

Yellow-bellied Marmot(s), Marmota flaviventris

Common throughout the class Mammalia, hibernation involves a profound change in behavior, morphology, and physiology as they undergo a remarkable phenotypic switch. Hibernation is one of the major forms of dormancy in mammals.  It is characterized by a prolonged winter reduction of metabolic rate and body temperature near ambient temperature. Another definition of hibernation is extended bouts of torpor where minimal body temperature can fall as low as -2.9°C. The factors that induce hibernation are still under discussion, but blood distribution is argued as one of the most important. Limited resources in terms of food, composition of food, cold, and the absence of external stimuli contribute to inducing hibernation. The external cues of seasonal influence, darkness, and CO2 concentration are not essential.

Torpor

♀ Broad-tailed Hummingbird, Selasphorus platycerus

Torpor, hibernation, and estivation are three major forms of dormancy that have been classified in mammals. The first, torpor, can be exhibited in a number of small mammals and birds, especially during cold nights or cold winter months. It may either be seasonal, or non-seasonal. The depth and duration of torpor vastly affects energy savings. While torpor can be defined as a substantial reduction in metabolic rate, body temperature, and other functions, the basics of torpor in mammals and birds has evolved separately. There is also variation between masses on whether the metabolic reduction is a temperature effect or a physiological inhibition.

The use of torpor also varies per species, and can rely on a number of factors. The migratory hummingbird retains the ability to enter nocturnal torpor all year round, but there is a strong seasonal component. For certain seasons, the use of torpor is for "energy emergencies" while at other times torpor may be used to minimize time needed for premigratory fattening.