Making the Bands
Standard bird
bands vary in diameter from about 0.3mm to 35mm, but hummingbird bands are a
whole different story. Their bands are so small they are photoengraved on a
flat sheet of aluminum that is so thin the bander must snip out or cut each one
separately. Here is a photo of what the sheet looks like before it is cut:
Cutting the band
Each tiny band is then bent around
a fixed pin as shown below
The miniscule bands are
carefully placed in a container for future use.
An individual hummingbird band weighs less than one-hundredth of a gram –
about 6-7 milligrams! By comparison to a hummingbird's weight, a band is
roughly equivalent to that of a gold wristwatch and band on a human, something
people get used to very quickly. Since hummers do not pick at bands after they
are applied it is probable the birds likewise become used to their new jewelry.
A properly applied band has no apparent effect on the bird's safety or behavior
and allows us to gather valuable information about hummingbirds that can be
acquired in no other way.
Hummingbird bands are issued only to banders who have received
specialized training for the banding techniques used for these tiny birds.
How to Band a Hummingbird
Banders are
always very gentle and careful with the tiny birds, although as
intercontinental migrants, hummers are tougher than they look.
The main
method of catching them is using a hummingbird net trap which is made of soft
mesh for safety. Nectar is placed inside the net which the hummers come to feel
on and then the net is dropped by using a hidden cord held some distance away.
There are
different ways banders use to secure the birds for the banding and taking of
various measurements. At RPBO we use mini “straight jackets” held by a small
clip.
To weigh a
hummer you use a medical scale, usually used for weighing tiny quantities of
drugs by pharmacists. A large hummingbird might weigh 4 grams.
The weight of
the birds tells the researchers about their ability to successfully complete
their long migration, as well as how well they are finding food on their
migration or locally.
How many
species are there in BC?
There are four: the Rufous, Anna's, Calliope & Black-chinned. In Victoria, we see Rufous (Selasphorus rufus) and Anna's (Calypte anna) hummingbirds at our feeders. Rufous are only here during the spring and summer, spending their winters on the U.S. Gulf coast and Mexico. Although an unusual sight fifteen years ago, Anna's are now winter regulars at many Victoria feeders. Feeders will not stop a bird migrating, a process that is triggered by the bird's internal clock and levels of sunshine. Anna's are with us year round and their presence at feeders has become more obvious because their numbers are increasing locally.
The Rufous has
the longest migration of any bird relative to its size. They over-winter in
Mexico and the Gulf states and breed from Washington State, through BC and into
Alaska. The males and females migrate separately, but both show extreme fidelity
to their migration routes. For example, the same bird is regularly caught at
the same feeder, about the same time each year.
Anna's Hummingbird
Black-chinned Hummingbird
Rufous Hummingbird
Calliope Hummingbird
Why do we need to monitor Hummingbirds?
Hummingbirds
are major pollinators across their range, with the migratory birds following
flowering northward in the spring and southward in the fall. In some regions
that hummingbirds visit, their contribution may be essential to survival of the
ecosystem. For an example that we all know in BC, let us consider their
importance to the salmon and bears of the Great Bear Rainforest.
The
hummingbird is a warm blooded pollinator and so unlike cold-blooded
invertebrates, which are less active in very cold conditions, hummingbirds can
withstand and function in the harsh/cold weather of early spring on the west
coast. As pollinators, they can provide a certain guaranteed level of fruit set
for early flowering plants like the salmonberry. These fruits are required by
the resident wildlife such as bears and wolves, to sustain themselves until the
salmon arrive. Salmon represent a substantial source of marine-derived nitrogen
that is required for the specialized types of forest that line salmon-bearing
waterways. As animals distribute fish carcasses and nitrogen-rich faeces into
the forest, they fertilize the soil, maintaining the type of vegetation
structure required for optimum flow and shading of the waterway, factors
essential and specific for each river's salmon. So, it is likely that
hummingbirds migrating all the way from Mexico play an important role in
maintaining the integrity of our coastal ecosystems.
Why band Hummingbirds?
Banding is an
effective methodology for studying population dynamics of birds. Hummingbirds
are one of the most species-rich avian families (Trochilidae, over 335 species)
in the world, yet have among the least information necessary for conservation
planning. Very little is known of many of the most basic population parameters,
such as population sizes and structure, demography, rates of species
hybridization, genetic diversity, and threats to persistence. Determination of
level of extinction threat and conservation planning requires such basic
knowledge of population biology.
The Rufous
Hummingbird (Selasphorus rufus) is a familiar sight in many parts of British
Columbia and Alberta, where it arrives during its annual northward migration
each spring; a number of the birds spend the winter in Mexico, others
overwinter along the Gulf Coast of the USA. Unfortunately, its numbers are
declining in several parts of its range in North America. The pattern of
decline is uneven, with some populations apparently stable from year to year,
while others show a reduction in the number birds returning each year. The aim
of the study (the Hummingbird Project of BC) is to determine whether or
not the birds that breed in British Columbia represent a single migratory
population, or whether the disparity in S. rufus numbers returning each spring
to different sites can be attributed to geographical differences in wintering
range between sub-populations. Using analysis of deuterium (a stable isotope of
hydrogen) in the feathers of migrating birds, it is possible to track the annual
migration of S. rufus with a degree of precision previously unavailable.
Deuterium levels in the environment can be predicted, with a gradient of
increasing concentration running from NW to SE in North America. Thus, isotopic
analysis of feathers allows us to determine the latitude at which an individual
bird was feeding at the time it was molting.
Threatened
hummingbird species in BC
Both the Rufous and Calliope hummingbirds are considered by Partners in Flight to be 'Species of Continental Concern'. This is because their numbers are declining, whether through habitat loss and increased stress or poor juvenile recruitment. Humans have modified the habitats that they migrate, over-winter and breed on. In addition, global warming will have a great effect on the flowering pattern that the birds rely on to travel up and down the continent. As we enter a warming phase, changes to water availability will impact the abundance of nectar resources, as well as the types of flora and timing of flowering. This could disrupt the wave of flowering that the hummingbirds follow and compromise their ability to migrate successfully.
