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Rufous Hummingbird: State of the Science and Conservation : simplebooklet.com

©VJAnderson
STATE OF THE SCIENCE AND CONSERVATION
RUFOUS
HUMMINGBIRD

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©Carlos Pacheco
Suggested Citation
Gillespie CR, Contreras-Martínez S, Bishop CA, Alexander JD. 2020. State of the Rufous
Hummingbird science and conservation. Western Hummingbird Partnership, Boulder, CO.
Caitlyn R Gillespie, Klamath Bird Observatory
Sarahy Contreras-Martínez, Universidad de Guadalajara-CUCSUR Autlán de Navarro
Christine A Bishop, Environment and Climate Change Canada
John D Alexander, Klamath Bird Observatory
Document design by Chu-Yu Lin
Author Ailiations
4
TABLE OF CONTENTS
©bryanhanson
RUFOUS HUMMINGBIRD:
STATE OF THE SCIENCE AND CONSERVATION
SOCIAL BEHAVIOR, PHYSIOLOGY, AND MORPHOLOGY
HABITAT USE DURING BREEDING AND POST-BREEDING MIGRATION
SPRING AND WINTER HABITAT USE
DISTURBANCE AND FIRE
FOOD RESOURCES AND POLLINATION
CLIMATE CHANGE AND PHENOLOGY
AGRICULTURAL PRACTICES, LAND USE, AND INVASIVE SPECIES
THREATS AND FULL LIFE CYCLE CONSERVATION
" NO REGRETS" CONSERVATION ACTIONS
REFERENCES
6
10
13
14
15
16
18
20
22
23
24
ACKNOWLEDGEMENTS
This project was a collaborative eort of the Western
Hummingbird Partnership and funded by US Forest Service
International Programs. Contributing Partners represent the
North American range of the Rufous Hummingbird, including
University of Guadalajara – CUCSUR in Mexico, Klamath Bird
Observatory, Environment for the Americas, US Forest Service,
Bureau of Land Management, and Point Blue Conservation
Science in the United States, and Environment and Climate
Change Canada in Canada. This document was improved by
reviews from Greg Butcher (US Forest Service) and Susan
Bonfield (Environment for the Americas). Layout coordination
and design was provided by Chu-Yu Lin (Environment for the
Americas). Photographs were contributed by Jim Livaudais,
Sarahy Contreras-Martínez, Gordon Leggett, Bryan Hanson,
Ugo Mendes Donelli, Zefe Wu, Chu-Yu Lin, Jonathan Moran,
Carlos Pacheco, Peter Neilsen, J Becky Matsubara, Larry
Jordon, Avia5, and VJ Anderson.
We recognize and acknowledge that the Rufous Hummingbird
migrates and breeds within the traditional territories of many
indigenous peoples throughout this species range.
5©Skeeze
6
Why a Review?
Rufous Hummingbirds are a
charismatic and remarkable migratory
bird, and through their role as
pollinators they provide important
ecological services across their range
in Canada, the United States, and
Mexico. There is a great opportunity
for concerned communities, bird
lovers, and conservation scientists
to rally together to develop a full life
cycle conservation strategy to protect
this long-distance migrant throughout
its entire range. This strategy should
include the ranking of threats, the
prioritization and implementation
of conservation strategies and
actions, and coordinated eorts
to fill information gaps, monitor
population trends and demographics,
and measure the eectiveness of our
conservation eorts.
In this Review
• Identification
• Social Behavior, Physiology, and Morphology
• Annual Migratory Cycle
• Habitat Use
• Disturbance and Fire
• Food Resources and Pollination
• Climate Change and Phenology
• Agricultural Practices, Land Use, and
Invasive Species
• Summary of Threats and Information Gaps
• “No Regrets” Conservation Actions
• References
• We review information about behavior, ecology, habitat needs, and threats throughout its
geographic range, including non-breeding areas in Mexico and southeastern United
States, breeding grounds in the Pacific Northwest, and the migratory stopover sites
in between.
• This document is intended to inform tri-national conservation planning and implementation
for this species, through which information needs, threats, and conservation opportunities
and strategies will be prioritized for action.
• We identify important information gaps along with threats and key conservation
opportunities throughout the full life cycle of Rufous Hummingbirds.
This report summarizes
the best available
information about the
biology and conservation of
Rufous Hummingbirds
(Selasphorus rufus)
©Jim Livaudais
RUFOUS HUMMINGBIRD:
STATE OF THE SCIENCE AND CONSERVATION
7
www.mbr-pwrc.usgs.gov
Percent Change per Year
Less than -1.5
-1.5 to -0.25
>-0.25 to 0.25
>0.25 to +1.5
Greater than +1.5
While still commonly observed throughout their range, Rufous Hummingbird populations are recognized
as an at-risk species.
1
Annual Breeding Bird Survey data indicate that their populations have declined by
as much as 60% since 1974.
1
While the causes of past declines are unclear, recent research indicates that
accelerated climate change could result in extensive range loss in the United States.
2
As a long-distance
migrant, Rufous Hummingbirds require high quality habitat across a large geographic area for breeding,
migratory stopovers, and wintering. Threats that may be factors in their population decline include the
impacts of climate change on food and habitat resources, loss of natural and traditional fire regimes, and
pesticide exposure. Because Rufous Hummingbirds likely encounter each of these threats repeatedly
throughout their annual life cycle, more information is required to understand how and to what extent
threats and stressors aect Rufous Hummingbirds in dierent geographic areas.
Addressing these threats to Rufous Hummingbirds, like many other migratory species, is limited by
information gaps about their breeding, migration, and wintering ecology. Details about their migration
and wintering areas are especially limited. Given its rapid population decline, our eorts to determine
the best approaches to coordinated research and population monitoring must accelerate and involve
conservation scientists, bird lovers, and concerned communities that can provide an important voice to
help advance the conservation of this species.
RUFOUS HUMMINGBIRD:
STATE OF THE SCIENCE AND CONSERVATION
Breeding Bird Survey Trend Map, 1966 - 2013
60%
decrease
since
1974
The Breeding Bird Survey (BBS) is a large-scale avian monitoring program that gathers data about North
American breeding bird population trends. Results from BBS data analyses show that Rufous Hummingbirds
are suering population declines throughout much of their breeding range.
8
Conservation Status
The Rufous Hummingbird is identified as a species
of continental concern on the North American
Watch List.
3
It also appears on the International
Union for Conservation of Nature (IUCN) Red List of
Threatened Species as Near Threatened.
4
Identification
Rufous Hummingbirds are among the smallest hummingbirds in the world, only 9-10 cm in length
5
with a body mass of about 3.5 grams – thats less than a nickel!
6
Named for their distinctive coloration,
male Rufous often have a solid rufous back, but many individuals have green back feathers and a
few (especially young ones) are more than half green. Their crown is bright green, while cheeks and
eyebrows and flanks are rufous. The adult male has a striking red gorget. The adult females are bright
green above and white below, however they still have strongly washed rufous on sides, flanks, and
undertail coverts to the edges of the rump. The face and sides of the female’s gorget are washed rufous.
The female gorget is creamy white but can be heavily spangled with green to bronze to iridescent red
feathers, which can vary from a few feathers to a small triangle or diamond.
Adult Male Rufous Hummingbird
©Avia5
rufous back but
may have some
flecks of green
rufous tail with black tips
rufous supercilium
rufous belly
brilliant red to
orange gorget
white breast
green back
rufous wash on
flanks
green crown
white throat heavily
spangled in dark
spots ; can have
a few to ~20-25
iridescent feathers
©Larry Jordan
white tips on the outer
three retrices of tail
bu-rust chest
Adult Female Rufous Hummingbird
Correct identification of Selasphorus hummingbirds requires knowledge of details in coloration and tail shape.
©Chu-Yu
9
Young or female Rufous Hummingbirds are diicult to identify
and can be confused with similar species such as Allens
Hummingbird (Selasphorus sasin).
Allen’s Hummingbird
©JBecky Matsubara
Distribution and population data for the Rufous Hummingbird can be complicated by incorrect
identification of Rufous females and young, which can closely resemble similar hummingbird species.
The immature Rufous males and females resemble adult females however the gorget on males is heavily
striped and can have a few iridescent markings. Key morphological features that distinguish Rufous from
Allen’s hummingbird (Selasphorus sasin) include the second tail feather on Rufous males that is distinctly
notched on the inner web near its tip; this feature is less noticeable but also present on female Rufous,
but not present on Allen’s. The male’s steep oval or J-shaped courtship display and courtship sounds the
Rufous males make are also distinctly dierent than Allen’s.
7,8
There is hybridization where the breeding
ranges of these two species overlap near the California-Oregon border.
9
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Rufous Hummingbirds are highly territorial at breeding, migratory stopover, and non-breeding sites. Male
Rufous Hummingbirds arrive on the breeding grounds before females where they establish territories and
perform flight displays.
10
When females arrive they choose nest sites, not necessarily within male flight
display territories.
10
Females exclusively build nests, incubate, and feed nestlings and fledglings. Nests
may be reused from year to year. Females may cluster their nests in concentrations of up to 20 within a
small area.
11,12
Males copulate with multiple females if they can and then leave breeding territories; they
may remain nearby for the season or move from coastal locations to interior or higher elevation locations
where they may establish new breeding territories.
13
Recapture rates of the Rufous Hummingbird reveal
that they can live for at least five years, with annual survival around 60%.
14
Annual
survival
rate around
60%
e oldest recorded Rufous Hummingbird
was nearly nine years old when she was
recaptured and rereleased during banding
operations in British Columbia.
8
SOCIAL BEHAVIOR, PHYSIOLOGY, AND MORPHOLOGY
©Peter Neilsen
40% of adults
don’t survive from
one year to the
next
11
Torpor
Hummingbirds seem to compensate for high elevations and low temperatures by increasing net energy
intake, likely through one or more behavioral modifications.
15
For example, Rufous Hummingbirds
conserve energy overnight by placing their bodies in a state of torpor (low-energy use, short-term
hibernation).
16
Torpor allows them to counteract for their small body size and energy loss in colder and
sometimes oxygen-poor (i.e., high-elevation) environments.
16–18
Information Gaps
More data is needed to understand how hummingbird morphology, physiology, and social behavior will
influence their ability to adapt to climate change and other stressors. For example, are drying conditions
changing nectar volumes and/or shifting ranges of high-elevation nectar resources and impacting
hummingbird populations? How will the unique behavioral and physiological characteristics that allow
Rufous Hummingbirds to breed in northern latitudes and persist in high elevations adapt to a changing
climate and multiple stressors at the same time?
©Jim Livaudais
Wing morphology
Hummingbirds often hover in flight,
a behavior that is energetically
demanding. Smaller wing sizes allow
for some of the territorial flight displays
of male Rufous Hummingbirds; female
Rufous have slightly larger wing sizes
than males.
19
12
Rufous Hummingbirds breed in coastal southeastern
Alaska south through southwestern Yukon, British
Columbia, southwestern Alberta, Washington,
northern and central Idaho, western Montana,
Oregon, and extreme northwestern California.
5
During southward migration, they stopover in
both the Pacific and Rocky Mountain flyways.
Males depart for southward migration initially and
generally follow a narrow path through the Rocky
Mountains. Within 1 to 2 weeks females then depart
and follow a broader southward route that includes
the Rockies and mountain ranges farther west.
Thereafter, juveniles migrate along the same route
as females but a greater number move south along
the eastern Sierra Nevada mountain range and even
further west in California.
20
They spend the non-
breeding season in coastal southern California and
Gulf Coast south to south central Mexico
5,21
and
more recently east along the northern coast of the
Gulf of Mexico. Adult males initiate spring migration
earlier than females
5
and mainly follow the Pacific
flyway through California northward.
21
©Carlos Pacheco
Annual Migratory Cycle –
An elliptical migration
Rufous Hummingbirds migrate north in spring along the
Pacific Coast to breeding sites in the northwestern United
States, Canada, and Alaska. Their return migration in
late summer and early fall follows the Rocky Mountains
before reaching Mexico.
66
Breeding season
Non-Breeding season
Pre-breeding migratory season
Post-breeding migratory season
Recaptures also show that some individuals may migrate from breeding sites in the northwest to wintering
areas in the southeastern United States, including Florida and Alabama.
67
13
Rufous Hummingbirds breed in second-growth forests and forest openings, as well as in mature forests,
riparian areas, parks, fields, meadows, and other open areas. In western Oregon, nests were found in
second growth forests from 16 to 120 years old.
22
Females build well-concealed nests in low branches of
trees and shrubs; nests are made of spider-webs and camouflaged with lichen. Rufous Hummingbirds
produce 1-2 broods per year and will return to nest sites and even re-use nests in following years.
11
During post-breeding migration, Rufous Hummingbirds use high-elevation alpine meadows, where late-
blooming nectar-producing flowers are abundant.
23
Hummingbirds will use a large diversity of flowers
including many that are not tubular or red.
24
Hummingbirds can visit four to five thousand flowers a
day.
24
Both males and females defend territories during southward migration; territory sizes vary widely
and are adjusted daily to maximize weight gain from nectar-producing flowers. Male territories tend to be
smaller and have denser flower availability, while female territories can be larger.
19
During the winter, Rufous Hummingbirds primarily occur in Mexican pine and pine-oak forests as well as
high mountain meadows. They are one of the most abundant pine-oak specialists across their wintering
range, regularly occurring with other hummingbirds including Mexican Violetear (Colibri thalassinus),
Rivoli's Hummingbird (Eugenes fulgens), Amethyst-throated Mountain-gem (Lampornis amethystinus),
Bumblebee Hummingbird (Atthis heloisa), Broad-tailed Hummingbird (Selasphorus platycercus), Calliope
Hummingbird (Selasphorus calliope), Berylline Hummingbird (Amazilia beryllina), and White-eared
Hummingbird (Hylocharis leucotis).
Annual population modeling and full life cycle conservation
Like many migrants, stressors that impact hummingbird populations at
one part of their range likely have cascading eects throughout their
annual migratory cycle. For example, limited food availability during spring
migration may delay spring breeding arrival or cause individuals to arrive
in poor condition, making it diicult to establish high-quality territories that
can support successful breeding.
12
Given their high metabolism, Rufous
Hummingbirds likely need abundant, reliable and pesticide-free food
resources to meet the energy demands of their long migrations. A full life
cycle approach to conservation of Rufous Hummingbirds must take into
account threats and opportunities throughout the annual migratory cycle
and at multiple geographic locations. Full life cycle analyses are needed
to reveal seasonal population limitation for the species and allow for more
focused conservation actions.
Visit
4000 - 5000
flowers
a day
HABITAT USE DURING BREEDING AND
POST-BREEDING MIGRATION
14
During winter, females and juveniles are more common at higher elevations, based on capture data
at sites 1900-3100m in Western Mexico, while adult male Rufous Hummingbirds appear to be more
common at lower elevations.
25
Human land-use often varies greatly by elevation, thus creating dierent
survival challenges.
Hummingbirds from dierent breeding subpopulations, in particular coastal versus interior, select distinct
sites during the non-breeding season in Mexico.
21
Evidence from isotope analysis suggests that females
from coastal breeding populations winter at higher elevations than males; but similar isotope dierences
were not observed for interior populations.
Relative abundance changes over time during the
winter. The magnitude of this change can depend on
the successional stage of forests and the abundance
of flowering plants.
Adults molt from December to February while
juveniles begin to molt shortly after arrival on
wintering grounds and can extend molting into spring
migration.
5
Molt is energy-expensive, and molting
season can be a diicult time for birds.
During spring migration, Rufous Hummingbirds
commonly use riparian habitats and low altitudes
where flowers bloom first in spring. Both male and
female individuals establish and defend distinct
territories around flowering plants.
26
Females can outnumber males at some spring migration stopover
sites on the central coast of California.
27
Rufous Hummingbirds seem to arrive in Alaska before flowers
bloom and are seen at sapsucker wells.
68
Do Rufous Hummingbirds move among sites during the non-breeding season, and if so why and how
far do they move? More information is needed on the sex- and age-specific movement and distribution
patterns during late fall, winter, and early spring. How do these movements aect survival? Detailed
information about migratory connectivity is also needed. For example, do individuals that winter in
dierent areas of Mexico come from distinct breeding areas in Alaska and western USA? Are there
dierences in the relative abundance, survival, or reproductive success that vary with successional state
of forested habitat?
SPRING AND WINTER HABITAT USE
Information Gaps
©Chu-Yu
15
While Rufous Hummingbirds nest in both second-growth forests and older mature forest, post-
disturbance mid- to early-successional habitats are important for breeding Rufous Hummingbirds.
Post-fire habitats provide stopover habitat for Rufous Hummingbirds in the Sierra Nevada during their
post-breeding migration; high numbers of migrating individuals have been observed when wildflowers
are abundant following wildfire events.
29
In the northern Rocky Mountains, studies demonstrate the
importance of post-fire habitat for a number of bird species, including hummingbirds.
30,31
It is also
possible that increasing fire frequency and intensity, as well as timing of fire, have had negative eects
on Rufous Hummingbird habitat and hence their populations. Reduced overall habitat availability at the
landscape scale not only reduces resource availability for migratory bird species but can alter stopover
habitat use.
During winter in Western Mexico, Rufous Hummingbirds utilize plants that regenerate post-fire, such as
sage (including Salvia iodantha and S. mexicana).
32
Fires maintain plant species diversity in pine and
pine-oak forests.
33
Recently disturbed or burned habitat is important to Rufous Hummingbirds, as is
a mosaic of dierent successional stages that primarily result from low-severity fires that occur every
11 to 30 years.
33
Small areas (<3 hectares) aected by high severity fire that are surrounded by later
successional forests are also important.
34
DISTURBANCE AND FIRE
Information Gaps
How do herbicide treatments specifically influence hummingbird populations? How does fire frequency,
intensity, and timing influence Rufous Hummingbird habitat use and survival throughout their range?
How have changes in land use and habitat loss on the breeding grounds, during stopover, and/or on the
wintering grounds influenced Rufous Hummingbird declines?
Because post-disturbance forest habitats are important for breeding Rufous
Hummingbirds, fire management that suppresses fires, or changes fire cycles
to occur more often and at higher intensity, may limit the availability of early-
successional post-fire habitat.
Fire
Management
Rufous Hummingbirds are abundant in timber stands immediately following
harvest when floral resources are able to flourish. Their abundance can
increase immediately after prescribed fire or logging,
35,36
but removal of
understory and shrub vegetation from these habitats may limit nesting and
foraging habitat. The use of herbicides to remove deciduous understory to
allow for ‘conifer release’ reduces the availability of wildflowers in forests,
Mixed-successional forest across landscapes may also be beneficial for
hummingbirds.
Timber
Management
©Sarahy Contreras
16
Nectar
Rufous Hummingbirds feed on nectar from a variety of plant species and move in correlation with floral
phenology throughout their range. In breeding and migratory stopover areas, typical flower species in
their diet includes red tubular species such as red columbine (Aquilegia formosa), scarlet gilia (Ipomopsis
aggregate), bearded tongues (Penstemon spp.), and paintbrushes (Castilleja spp.). They will also drink
nectar from a variety of other flowers including sage (Salvia spp.), bouvardia (Bouvardia ternifolia), mint
(Stachys coccinea), lilies (Erythronium grandiflorum, Lilium columbianum), purple larkspur (Delphinium
barbeyi and D. geranioides), heath (Vaccinium ovatum, Menziesia ferruginea), currant (Ribes sanguineum),
salmonberry (Rubus spectabilis), honeysuckle (Lonicera spp.), fireweed (Epilobium angustifolium),
horsemint (Monarda menthifolia), toad-flax (Linaria vulgaris), snapdragon (Scrophularia montana), and
bee-flower (Cleome serrulata).
10,28,37–41
In Mexico, presence of Rufous Hummingbird coincides with the
flowering peak coincides with peak flowering of the plant genera Salvia, Lobelia, Calliandra, Ipomea, and
Senecio.
25,32,42,43
©Jonathan Moran
FOOD RESOURCES AND POLLINATION
17
Habitat and resource selection
How do Rufous Hummingbirds find
flowers? While Rufous Hummingbirds
return to known food sources, nectar
from many dierent plant species is a less
predictable yet important food resource.
Rufous Hummingbirds use memory
of previous foraging locations to find
food sources more eiciently.
48
Rufous
Hummingbirds also rely on visual cues
to find food sources.
49
Large patches of
blooming flowers are necessary to sustain
Rufous hummingbird territories. Individuals
maximize energy intake and may make
daily adjustments to defend territory
size.
23
When flower numbers are reduced
or destroyed by natural events, such as
storms, Rufous Hummingbirds appear to
leave the immediate area rather than settle
into smaller or lower-quality territories.
50
While it is likely that hummingbirds act as pollinators on the wintering grounds, more research is needed
to understand this important ecological role.
25
In the spring, Rufous Hummingbirds act as pollinators for
early blooming nectar-producing plants.
44
Insects
Insects such as gnats and aphids are consumed by Rufous Hummingbirds on their breeding grounds
and throughout their life cycle but are particularly important as a food source for growing chicks.
45
Insects also provide protein, an essential nutrient not found in nectar and needed for feather growth
during molt.
Other food resources
While nectar-producing flowers are clearly an important food source, other sources are important in
the diet of Rufous Hummingbirds. Early spring migrants may supplement their nectar-based diet with
alternate food sources; some will feed on sap from sapsucker wells as a source of sugar.
46
Calcium, an
important nutrient for breeding females, does not occur naturally in nectar; calcium deposits from ash
or soil near nest sites serve as a necessary mineral supplement
47
and insects may also be a source of
minerals.
FOOD RESOURCES AND POLLINATION
©Chu-Yu
18
CLIMATE CHANGE AND PHENOLOGY
Southward migration
Warming temperatures and reduced snowpack in montane meadows have resulted in earlier flowering
phenology in some plant species. Montane meadows in the Rocky Mountains have seen a reduction in
mid-summer (July-August) flower abundance, which may aect pollinators including hummingbirds.
55
Non-breeding/wintering
In Mexico, Rufous Hummingbirds undergo a complete molt on their wintering grounds,
56
an important
and energetically taxing life-history event. Changes in the peak flowering phenology of hummingbird-
associated plant species or declines in insect populations during this time could threaten Rufous
Hummingbirds.
Northward migration
During northward migration, early spring migrants may compete for limited resources that are aected
by climate change and related phenology shifts in the flowering of nectar-producing plants.
Breeding
Spring arrival of Rufous Hummingbirds in the northern parts of their breeding range have shifted earlier
in the last 10 years
.53
Breeding success will likely depend on corresponding shifts in local floral and insect
phenology, although research is still needed to quantify potential mismatches in local resource phenology
across the breeding ranges. Declines in insect populations
,54
in addition to climate-related shifts in
phenology, have the potential to impact food sources for chicks.
Rufous Hummingbird migration is closely timed with floral phenology; however, it is possible that shifts
in local resource phenology may now be out of sync due to shifts in timing of migration as a result
of accelerated climate change. Flowering phenology across habitats and elevations may be aected
dierently by climate change in local temperature and precipitation regimes. Changes in the availability
of resources could alter hummingbird habitat selection and migratory stopover behavior.
51
Uneven
changes in resource availability across geographies may impact Rufous Hummingbird survival at multiple
times throughout the full life cycle and contribute to population declines.
52
©Sarahy Contreras
19
Information Gaps
While climate-related changes in habitat, resource, and migration phenology have the potential to impact
Rufous Hummingbird populations, more research that builds on existing climate and bird conservation
science is needed.
2
Future warming will require many species to shift to northern latitudes or to higher
elevations, but are there physiological constraints on Rufous Hummingbirds that would prevent similar
range shifts? Climate change may produce long-term drought in current areas important to Rufous
Hummingbirds, which may increase fire severity. Where is drought predicted, and how might this aect
Rufous Hummingbirds? Climate-smart natural resource management that takes into account projections
of future climate change scenarios may help mitigate some potential impacts of climate change on
hummingbird populations. For example, landscape-level conservation planning may be able to prioritize
forest management for hummingbirds within their expected range under future climate change scenarios.
CLIMATE CHANGE AND PHENOLOGY
Phenology
describes the timing of
events in nature, such as the
flowering of plants or the arrival
of migrants. The natural cycles of
events rely on cues such as day length or
temperature. Because climate change may
aect the cues in dierent ways, a “mismatch
of timing of events that were historically
aligned can occur. When this happens, migrants
may arrive “too late for dinner” if nectar
producing plants flower earlier than normal.
For example, plants are now blooming earlier
than the arrival of Broad-tailed Hummingbirds
(Selasphorus platycercus) in the northern part
of their breeding range.
30
©Sarahy Contreras
20
Pesticides
The eects of herbicide and insecticide use on Rufous Hummingbirds and
the habitats and nectar-producing plants they rely on is an important and
growing area of research. Exposure to widely-used systemic insecticides
occurs in Rufous Hummingbirds.
5 7, 5 8 ,65
Neonicotinoids from nectar or
pollen have been known to aect pollinating insects
59
and may represent
a threat to birds as well.
60
Pesticide exposure may have direct health
eects on hummingbirds, similar to eects described in songbirds,
61
but
may also have indirect eects on hummingbirds by diminishing their food
resources throughout their range.
AGRICULTURAL PRACTICES, LAND USE, AND
INVASIVE SPECIES
Grazing and Agricultural Practices
Loss of wildflower resources in forested habitats due to ungulate grazing remains unquantified. Overgrazing
by ungulates removes many floral resources, but some may persist if not preferred by the grazers. Thus, the
extent to which grazing reduces food for hummingbirds on a landscape scale is unknown. The conversion of
native meadows and openings to non-native grasses, which reduces forbs and nectar-producing plants, may
also reduce the availability of floral resources.
©zefe wu
©Ugo Mendes Donelli
21
Information Gaps
How does habitat alteration from agricultural development, cattle grazing, and pesticide use aect Rufous
Hummingbirds throughout their range?
25
Invasive Species
Invasive plants, especially grasses, outcompete
native flowering plants in alpine meadows
throughout the southward migratory route of Rufous
Hummingbirds, potentially reducing food availability
during energetically demanding migration at high
altitudes.
62
Invasive plant species that outcompete
native wildflowers may have incorrectly timed
phenology patterns for migrating hummingbirds. For
example, the invasive Himalayan blackberry (Rubus
armeniacus) outcompetes Salmonberry (Rubus
spectabilis) in riparian habitats. Salmonberry is native
and blooms in early spring throughout its range
and is a typical Rufous Hummingbird food source in
migration. Himalayan blackberry blooms later in the
spring,
63
after Rufous Hummingbirds have arrived on
breeding grounds.
Development
Rural and urban development removes native
wildflowers. While Rufous Hummingbirds will
utilize gardens and feeders during migration,
those resources expose hummingbirds to other
threats such as predation from cats and window
collisions.
5
With increased availability of land
cover data, it may be possible to determine
if changes in land use can account for the
observed declines in Rufous Hummingbirds
over the past 50 years. This information may
be useful in quantifying hummingbird pesticide
exposure by mapping changes in agricultural
types and acreages across the range of Rufous
Hummingbirds.
©Gordon.Leggett.2018
©Bryan Hanson
22
The Rufous Hummingbird is a long-distant migrant
with declining populations. While still common
in some parts of its range, breeding bird survey
data suggest that there are 60% fewer Rufous
Hummingbirds now than there were in the early
1970s. If this trend continues we may lose another
50% of the population by 2050.
1
As a result, this
species is widely recognized as an at-risk species.
Like many migratory birds, Rufous Hummingbirds
face threats throughout their full life cycle – they face
threats on their wintering grounds in Mexico, on their
breeding grounds in northwestern North America,
and at stopover sites that they depend on as they
make their spring and fall migrations. Climate change
could impact key elements of their life history and
food resources as increased temperatures, drought,
fire-changed habitats, and phenological mismatches
occur between flowers and birds. Lack of natural and traditional fire regimes, invasive species,
overgrazing, forestry practices, and pesticides all contribute to loss of floral resources and habitat. These
stressors can impact all species of hummingbirds; but because Rufous Hummingbirds migrate the
furthest among all species of hummingbirds, they may be especially vulnerable to changes that occur
in multiple geographic locations throughout their life cycle. They may be a useful umbrella species for
other western hummingbirds and for other western pollinators, and thus the Western Hummingbird
Partnership (https://westernhummingbird.org/) has prioritized the study of Rufous Hummingbird.
An important next step in developing a full-life-cycle conservation strategy for western hummingbirds
is to conduct an assessment of threats on the Rufous Hummingbird specifically. A broader threats
assessment for migratory and resident western forest birds identified unsustainable agricultural
expansion and practices, unsustainable livestock farming/ranching expansion and practices,
unsustainable logging and wood harvesting, disruption of natural disturbance regimes, water
management and altered hydrology, and inadequate forest restoration as the most significant threats.
64
Which of these are the most significant threats to the Rufous Hummingbird, and are there important
threats not included in this list?
Despite population declines and apparent threats, we still lack critical information about Rufous
Hummingbirds that will be needed to address these conservation issues. Information gaps about their
breeding, migration, and wintering ecology remain broad and more information about their migration and
wintering area habitat preferences is especially needed. Research on the eects of climate change and
pesticide use, as detailed above, will also fill critical information gaps. Better information on survival and
reproductive rates (and factors that aect these rates) will contribute important quantitative information.
THREATS AND FULL LIFE CYCLE CONSERVATION
Winter Range
Breeding Range
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23
While we continue to improve our knowledge of these species, we need to undertake conservation
now because Rufous Hummingbirds - along with other pollinators – are already declining. We know
that all pollinators are completely dependent on flower availability throughout the year. We also know
that many changes over the past 50 years have diminished the availability of flowers. Thus, the Western
Hummingbird Partnership is focused on increasing flower abundance and diversity throughout the
ranges of these hummingbird species. Native, locally adapted flowers are important for pollinators, and
conservation eorts should focus on increasing the abundance and diversity of native plants whenever
possible. Such conservation action must use climate-smart approaches that consider ongoing range
shifts in flowering plants.
Science-driven conservation works – there are many examples that demonstrate how at-risk species
can be recovered when our society chooses to invest in their conservation. With this State of the
Rufous Hummingbird Science and Conservation review we sound a call to action for the full-life-cycle
conservation of western hummingbirds using the Rufous Hummingbird as the lead example.
" NO REGRETS" CONSERVATION ACTIONS
©Sarahy Contreras
24
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©Jim Livaudais
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