POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
164
3. THE STATUS AND TRENDS IN POLLINATORS
AND POLLINATION
there are extensive records available of the phenology of
their migration in the USA and Canada, as observers across
a large latitudinal gradient report their first sightings each
spring (e.g., http://www.hummingbirds.net/map.html).
Habitat loss in their overwintering and summer breeding
grounds, and in the migration corridor, may pose threats to
the migratory species, and there is the potential for effects of
climate change on flowering phenology that may also create
challenges for phenology of migration (McKinney et al.,
2012). Hummingbirds are most diverse in the Neotropical
and important pollinators of that flora, but information on
population trends are completely lacking.
Bird occurrence has been monitored in South Africa in two
large citizen science projects, the first Southern African
Bird Atlas Project (SABAP1: 1987-1991) and the second
Southern African Bird Atlas Project (SABAP2: 2007-present);
data at http://www.gbif.org/dataset/282d0ccb-4fa0-
40f9-8593-105c77e88417. A recent comparison of these
two data sets finds that the families Pycnonotidae and
Ploceidae, which include nectar as a small component of
their diet, have increased in abundance in 66% and 61%
of geographical grid cells respectively, whereas the families
Nectariniidae (Sunbirds) and Promeropidae (Sugarbirds),
both of which include nectar as a major component of
their diet, have increased in 52% and 33% of grid cells
respectively. Because very few grid cells remain unchanged,
these data indicated that the Promeropidae show a decline
in about 67% of grid cells (Loftie-Eaton, 2014).
Bats are another important and diverse group of vertebrate
pollinators in many parts of the world (Fleming and Mucchala,
2008). Population estimates are available for a few species
of pollinating bats, but in general little is known about
trends, in part because they are difficult to survey (http://
digitalcommons.unl.edu/usgsstaffpub/35/). In some areas
bats are important pollinators of food resources, such as
cactus fruits in Mexico (Arias-Cóyotl et al., 2006), agave
species (including those used for tequila and mezcal) (Rocha,
2005; Trejo-Salazar et al., 2015), species of mango, wild
species of banana, durian, and guava (http://www.bats.org.
uk/pages/why_bats_matter.html). The migratory species in
Central and North America face many of the same challenges
described above for migratory hummingbirds, as well as the
additional constraint of needing caves for roosting (Slauson,
2000). One study found that an island population of a
columnar cactus may be moving toward insect pollination
because of a paucity of bats, possibly a consequence of
hurricanes (Rivera-Marchand and Ackerman, 2006).
Pollinator extinction, reintroduction, and
replacement
Local and global extinctions of pollinators have occurred
(Cox and Elmqvist, 2000; Cameron et al., 2011), and some
conservation efforts have been implemented to re-introduce
missing species or replace their functions as pollinators.
An example of re-introduction (See Chapter 6 for additional
information on re-introductions) is the case of the United
Kingdom bumble bee species Bombus subterraneus, which
was declared extinct in the UK in 2000. An initial attempt
to use queens from New Zealand in 2011 for reintroduction
was unsuccessful (Howlett et al., 2009). However, a
subsequent programme to reintroduce B. subterraneus
with queens from Sweden is ongoing following restoration
of appropriate habitat and food plants (Gammans, 2013),
and although workers have been observed, production
and successful overwintering of queens has not yet been
proved. This re-introduction protocol developed for B.
subterraneus in the UK may be useful in other parts of
the world experiencing similar bumble bee extinctions
(e.g., B. occidentalis in parts of its former range in North
America) (Cameron et al., 2011). A fortuitous replacement
of pollination occurred in Hawaii, where the introduced
Japanese White-eye (Zosterops japonica) assumed the
role of extinct bird species as a pollinator of the ieie vine
(Freycinetia arborea) (Cox, 1983).
The current status of almost all wild pollinator populations
is unclear and difficult to assess due to the lack of data.
TABLE 3.1
Data on migratory hummingbird population trends from 1966 – 2012 from the Breeding Bird Survey data from USA and
Canada. Means for number of birds observed per survey route are shown with 95% Confidence Intervals.
From http://www.mbr-pwrc.usgs.gov/bbs/ (data retrieved 15 September 2015).
Common name Species USA annual trend (N) Canada annual trend (N)
Ruby-throated Hummingbird Archilochus colubris +1.6 (1,910) CI 1.3 – 1.8 +2.2 (387) first yr 1968 CI 1.3
– 3.0
Black-chinned Hummingbird Archilochus alexandri +1.1 (418) CI 0.2 – 1.9 +0.2 (10) CI -5.4 – 6.6
Anna's Hummingbird Calypte anna +2.0 (220) CI 1.3 – 2.7
Costa's Hummingbird Calypte costae -1.9 (99) CI -6.0 – 1.1
Calliope Hummingbird Stellula calliope -1.0 (168) CI -2.3 – 0.2 0.9 (52) CI -0.6 – 2.5
Rufous Hummingbird Selasphorus rufus -2.3 (214) CI -3.0 – -1.5 -1.9 (131) CI -3.1 – -1.6
Allen's Hummingbird Selasphorus sasin -4.1 (55) CI -5.7 – - 2.6