ArticlePDF Available

Establishing songbird nest boxes increased avian insectivores and reduced herbivorous arthropods in a Californian vineyard, USA

Authors:

Abstract and Figures

California winegrape growers interested in merging conservation with agricultural production have established nest boxes for songbirds in their vineyards. A common occupant, the native western bluebird Sialia mexicana consumes arthropods during the breeding season. We measured the effect of enhanced avian activity on arthropod pests and natural enemies by experimentally establishing songbird nest boxes in one section of a 50 ha vineyard. During avian brood production and shoot extension of the grapevines, we compared the composition of the arthropod community in the nest box area with that of a no-nest box control area. During peak nest box occupancy, the nest box area had significantly fewer herbivorous arthropods, including leafhopper pests, than the control area. There were also significantly fewer large, beneficial, predatory arthropods in the nest box treatment compared to the control area. After chicks hatched, small arthropods decreased in the nest box treatment area, while increasing in the control area. Therefore, although avian foraging near nest boxes reduced the abundance of beneficial arthropods, harmful herbivorous insects did not increase in the nest box treatment even when they increased in the control area. This indicates an overall positive effect of nest box provision on pest abundance in a large, commercial vineyard.
Content may be subject to copyright.
J.A. Jedlicka, D.K. Letourneau & T.M. Cornelisse / Conservation Evidence (2014) 11, 34-38
34
ISSN 1758-2067
Establishing songbird nest boxes increased avian insectivores and reduced herbivorous
arthropods in a Californian vineyard, USA
Julie A. Jedlicka1,2*, Deborah K. Letourneau1 & Tara M. Cornelisse3
1 Department of Environmental Studies, University of California, 1156 High St., Santa Cruz, CA, 95064, USA
2 Current Address: Department of Environmental Science, Policy, and Management, 130 Mulford Hall, University of California, Berkeley, CA,
94720, USA
3 Center for Biodiversity and Conservation, American Museum of Natural History, Central Park West at 79th St., New York, New York 10024, USA
SUMMARY
California winegrape growers interested in merging conservation with agricultural production have
established nest boxes for songbirds in their vineyards. A common occupant, the native western
bluebird Sialia mexicana consumes arthropods during the breeding season. We measured the effect of
enhanced avian activity on arthropod pests and natural enemies by experimentally establishing
songbird nest boxes in one section of a 50 ha vineyard. During avian brood production and shoot
extension of the grapevines, we compared the composition of the arthropod community in the nest box
area with that of a no-nest box control area. During peak nest box occupancy, the nest box area had
significantly fewer herbivorous arthropods, including leafhopper pests, than the control area. There
were also significantly fewer large, beneficial, predatory arthropods in the nest box treatment
compared to the control area. After chicks hatched, small arthropods decreased in the nest box
treatment area, while increasing in the control area. Therefore, although avian foraging near nest boxes
reduced the abundance of beneficial arthropods, harmful herbivorous insects did not increase in the
nest box treatment even when they increased in the control area. This indicates an overall positive
effect of nest box provision on pest abundance in a large, commercial vineyard.
BACKGROUND
Since the 1950s, over one million acres of oak woodland
has been converted to urban and agricultural lands in
California (Merenlender & Crawford 1998, Heaton &
Merenlender 2000). As a result, many cavity-nesting songbirds
have lost nesting sites and populations have decreased
(Partners in Flight 2002). In vineyard landscapes, some
concerned owners are attempting to merge avian conservation
with agricultural production by providing songbird nest boxes
on their land. The California grape growing season overlaps
with the migratory bird breeding season, which, due to the
energetic demands of reproductive activities, can result in
increased predatory pressure on arthropods (Holmes 1990).
Thus, it is possible that breeding birds may offer growers
ecosystem services in the form of insect pest control (Van Bael
et al. 2008), or ecosystem disservices by consuming predatory
insects important for pest regulation (Mooney et al. 2010).
Economically significant vineyard pests include
leafhoppers and sharpshooters (Hemiptera: Cicadellidae).
Some leafhopper and sharpshooter species such as the blue-
green sharpshooter Graphocephala atropunctata transmit the
bacterium Xylella fastidiosa that causes Pierce’s disease, which
can kill grapevines if infected in April and May (Feil et al.
2003). Consequently, reducing leafhopper pests in early spring
is beneficial to growers.
Western bluebirds Sialia mexicana are the principal nest
box occupant in California vineyards (Heaton et al. 2008).
* To whom correspondence should be addressed: julie.jedlicka@gmail.com
They are generalist insectivores and foraging by bluebirds has
been shown to significantly reduce sentinel pest larvae
(Lepidoptera: Noctuidae) in vineyards with artificial nest boxes
(Jedlicka et al. 2011). However it is unknown how bluebird
foraging affects other vineyard arthropods, including pests and
beneficial insects.
In this study we experimentally increased the abundance of
avian insectivores (bluebirds) by establishing songbird nest
boxes, and compared the type and abundance of arthropods
present with those in a control area without nest boxes. We
tested three questions: (1) do avian insectivores suppress
herbivorous insects and specifically reduce leafhopper pest
abundance near occupied nest boxes? (2) does avian foraging
lower the abundance of beneficial insects? and (3) do avian
insectivores target prey based on size?
ACTION
Study site: The 50 ha vineyard chosen for this experiment was
adjacent to the Russian River in Mendocino County, CA, USA,
near Ukiah (39°04'N, 123°09'W). Chardonnay grapevines were
planted in 1988, grown on trellises forming rows, and certified
organic since 1998. Tilling occurred in every other tractor row,
alternating with cultivated cover crops.
Nest box treatment: The vineyard was divided into three
sections. The 12 ha areas at each end were randomly assigned
as the control and conservation (nest box) treatments. A 250 m
wide middle section acted as a buffer between the treatment
and control, and no sampling took place in this area (Jedlicka
J.A. Jedlicka, D.K. Letourneau & T.M. Cornelisse / Conservation Evidence (2014) 11, 34-38
35
ISSN 1758-2067
et al. 2011). Nest boxes were constructed from redwood
following recommendations of the North American Bluebird
Society (2008) (13.9 x 10.2 x 23.8 cm, with entrance hole
opening of 3.8 cm diameter). In January 2008, 23 pairs of nest
boxes were established in the conservation treatment area in a
grid pattern of five rows. Each row consisted of three to six
pairs of boxes on 3.1 m t-posts along grapevine trellises. All
nest boxes were cleaned of previous reproductive materials in
February 2009 and checked weekly for nesting activity during
the 2009 bluebird reproductive season from March through
July. Once nest boxes were found to contain eggs, Noel
predator guards made of wire mesh hardware cloth (Toops
1994) were attached to the outside of the boxes to prevent
predation by raccoons Procyon lotor and domestic cats Felis
catus.
Arthropod Sampling: Arthropods were vacuum sampled from
the cover crops growing between grapevine rows at five
randomly selected points in the nest box treatment area (nest
box area) and at five randomly selected points in the control
area (control area). Arthropod sampling occurred during a two-
week period before (5 May) and during (19 May) the peak
avian foraging times of the 2009 breeding season. Vacuuming
lasted 20 s per sample using a Stihl BG 85 hand-held machine.
Contents were collected in an internal mesh bag (Osborne &
Allen 1999), emptied into plastic bags containing cotton balls
and ethyl acetate, and stored in a -20°C freezer until examined.
Arthropods were identified to order, family, or as commonly
known species. We measured the body length of each
specimen to the nearest millimeter, unless there were more
than 10 individuals in a family, in which case we measured the
lengths of 10 representative individuals. We recorded the total
number of individuals, functional guilds (predator, herbivore,
parasitoid, or other), and representative lengths for each
sample. Arthropods measuring over 5 mm were classified as
large, under 2 mm were small, and between 2-5 mm were
medium.
Data analysis: We conducted two-way ANOVAs (SAS Inc.,
V. 9.2) on arthropod guild, size categories, and selected insect
families. Main effects were site (two levels: nest box and
control areas), time (two levels: 5 May and 19 May), and time
Table 1. Average abundance (mean ± S.E.) of arthropod taxa and size classes per vacuum sample in a treatment area with nest
boxes and a control area at two dates in May. Uncommon taxa are listed below the table.
Taxon
Guild
Common
Name
Average
length (mm)
Nest box area
Control area
5 May
5 May
Aphididae
herbivore
aphids
1.3
41.8 ± 10.1
14 ± 3.3
Chironomidae
herbivore
midges
1.5
0.4 ± 0.9
1.4 ± 0.9
Chrysomelidae
predator
clover flea
beetles
2.2
18.6 ± 4.1
5.6 ± 1.3
Coccinelidae
predator
ladybird
beetles
5.6
1.2 ± 0.4
4.8 ± 1.0
Curculionidae
herbivore
weevils
5.1
2.0 ± 0.7
0.8 ± 0.4
Drosophilidae
herbivore
fruit flies
1.9
10.8 ± 3.0
8.0 ± 1.3
Elateridae
herbivore
click beetles
5.2
1.8 ± 0.7
4.6 ± 2.7
Lygaeidae
herbivore
false chinch
bugs
4.2
0.4 ± 0.4
0
Aranidae
predator
orb-weaving
spiders
4.4
1.2 ± 1.2
0
Carabidae
predator
ground beetles
3.7
1.0 ± 0.8
1.6 ± 1.0
Formicidae
predator
ants
4.8
3.2 ± 0.7
2.0 ± 0.9
Isopoda
other
pill bugs
5.1
2.8 ± 1.9
19 ± 6.5
Ichneumonidae
parasitoid
Ichneumon
wasps
3.9
3.2 ± 1.0
2.0 ± 0.5
Small taxa
< 2
37 ± 4.3
17 ± 2.3
Medium taxa
2 - 5
37 ± 9.0
22 ± 1.9
Large taxa
> 5
10 ± 1.9
32 ± 5.6
Uncommon taxa in vacuum samples (< 6 individuals): Acari, Acrididae, Apidae, Berytidae, Chilopoda, Coreidae, Dermaptera,
Diplopoda, Unknown Diptera, other Hemiptera, Lepidoptera, Lycosidae, Meloidae, Miridae, Mordellidea, Muscidae, Neuroptera,
Pentatomidae, Psocodea (Psocoptera), Reduviidae, Salticidae, Sarcophagidae, Scarabaeidae, Siphonaptera, Tenthredinidae,
Thomisidae, and Tipulidae.
J.A. Jedlicka, D.K. Letourneau & T.M. Cornelisse / Conservation Evidence (2014) 11, 34-38
36
ISSN 1758-2067
by treatment interaction. When variables were normally
distributed we used raw arthropod abundances and when data
Hto compare average lengths of arthropods within each
foraging guild because homogeneity of variance assumptions
were not met. Kruskal-Wallis tests were used to compare the
size differences among all groups followed by Mann-Whitney
U test for pairwise comparisons, with Bonferroni corrections
for multiple tests (adjusted alpha-value at 0.017).
CONSEQUENCES
Insectivorous birds: During the breeding season, 23 active
bluebird nests were found in the nest boxes established in the
conservation treatment. On average, nests contained 4.2
nestlings (S.E. = 0.21, range two to six). The earliest hatchlings
were found on 7 May with populations peaking on 21 May (n =
69 nestlings; Figure 1A). There was a clear decline of nestling
abundance in late May when first broods fledged. Bluebirds are
obligate cavity nesters and no bluebird nests were located in
the control area of the vineyard.
Arthropod prey populations: A total of 3,252 arthropods
were collected and showed a pattern of decreasing abundance
with time as bluebird foraging increased to provision nestlings
(mean ± S.E.: 108.2 ± 7.3 arthropods per sample on 5 May vs.
67.7 ± 13.0 on 19 May). This decrease in arthropod abundance
occurred in the nest box treatment (from mean ± S.E. 84.4 ±
14.9 to 34.0 ± 18.5) but not in the control area (from mean ±
S.E. 71.2 ± 4.9 to 86.6 ± 14.9; date by treatment interaction
Fdf=1 = 5.4, p = 0.034). Several pest and beneficial arthropod
taxa increased in abundance with time in the control area,
while simultaneously becoming scarcer in the section of the
vineyard with bluebird nestlings (Table 1, Figures 1A-B).
Figure 1. Average (± S.E.) abundances of arthropods grouped as: A) leafhoppers, B) herbivorous arthropods, C) predaceous
arthropods, and D) large arthropods (>5 mm in body length), captured in vacuum samples taken before (5 May) and after (19
May) peak brood hatch in the nest box area and control area of the vineyard. Line in Figure 1A shows total western bluebird
nestling abundance in nest boxes in the conservation treatment area during the breeding season.
Figure 1A.
Figure 1C.
Figure 1B.
Figure 1D.
J.A. Jedlicka, D.K. Letourneau & T.M. Cornelisse / Conservation Evidence (2014) 11, 34-38
37
ISSN 1758-2067
Mean abundances of the less common taxa represented in
vacuum samples, including herbivores, predators, ichneumon
wasps, and isopods are shown with occasional captures listed
below Table 1.
Herbivores in 18 families comprised the majority (70%) of
the arthropods sampled (Table 1, Figure 1), including aphids
(Aphidae), leafhoppers (including vineyard pests), and clover
flea beetles (Chrysomelidae). By the time of peak nestling
abundance in the nest box treatment (21 May) leafhopper
abundance had decreased by over 50% on average, compared
to a simultaneous threefold increase in the control area (Figure
1A), leading to a significant time by treatment interaction (Fdf=1
= 5.8, p = 0.028). Other herbivorous insects (e.g. chrysomelids
and aphids) showed a similar pattern of abundance to
leafhoppers (Figure 1B; Table 1), with significant time by
treatment interactions (Fdf=1 = 8.0, p = 0.012)
Predaceous arthropods were half as abundant in the nest
box treatment as in the control area (Figure 1C; mean ± S.E.:
17.6 ± 2.1 per sample vs. 9.3 ± 2.1 S.E., Fdf=1 = 10.1, p = 0.006,
p > 0.10 for time and for the interaction term). Predatory
ground beetles (carabidae) and ladybird beetles (Coccinelidae)
(Table 1) showed this same pattern. Parasitoids, which were
less abundant than other groups, were not significantly
different between treatment and control areas (mean of
approximately three individuals per sample in treatment and
control during both time periods, p > 0.05 for treatment, time,
and the interaction term).
Abundance of arthropods larger than 5 mm in length (large
arthropods), regardless of guild, was significantly higher in the
control area than the nest box treatment during both sampling
periods (treatment effect Fdf=1 = 32.3, p < 0.001; Table 1).
Large arthropod abundance significantly decreased by a factor
of about three in both the control and nest box area over the
two weeks in May (time effect Fdf=1 = 23.7, p < 0.001, Figure
1D). In early May the abundance of both small (those under
2mm) and medium (2-5mm) bodied arthropods increased in the
control area while simultaneously decreasing in the nest box
treatment (Fdf=1 = 21.2, p < 0.001). The average length of
predators was significantly greater than the average size of
herbivores (Mann-Whitney U = 4010, Z = -8.5, p < 0.001)
although some herbivores such as cicadellids, curculionids,
elaterids, and root feeders/detritivores were > 5 mm (Table 1).
DISCUSSION
Do avian insectivores suppress herbivorous insects and
specifically reduce leafhopper pest abundance near occupied
nest boxes? Variation in arthropod abundances indicated that
the addition of nest boxes increased local foraging by
bluebirds, reducing the number of arthropods that colonised
vines during shoot extension and leaf expansion. Abundances
of herbivorous arthropods, including leafhopper pests, declined
significantly in areas with songbird nest boxes while numbers
rose in areas without artificial nest boxes. By early June,
leafhopper abundance in the control areas of the vineyard
prompted the grower to spray a broad-spectrum pesticide.
Leafhopper pests are known not to be controlled adequately by
arthropod predators, parasitoids, or cover cropping practices,
especially in the early spring (Costello & Daane 2003); thus it
is promising that the provision of nest boxes reduced
leafhopper populations during this critical period of vine leaf-
out and shoot extension. Potential pests of cover crops (leaf
beetles and aphids) also exhibited declines in abundance
associated with the presence of nest boxes, suggesting that
insectivorous birds feeding and raising young can provide
additional benefits.
Does avian foraging lower the abundance of beneficial
insects? We did not detect any impact of avian predation on
abundances of adult parasitoids, which some growers use for
biological control of pest insects. However, we found evidence
that birds do lower the abundance of insect predators of
herbivores. Two families of predatory arthropods (ladybird
beetles and carabid ground beetles) declined in abundance near
bird nest boxes. It is possible that avian foraging directly
caused lower abundances of these families, but ladybird beetles
are known to be unpalatable to many predators because they
synthesize noxious chemicals in their body fluid (Glisan King
& Meinwald 1996). Alternatively, ladybird beetles may have
concentrated in control areas that offered more aphid prey
(Triplehorn & Johnson 2005). Regardless, the reduction in
predaceous arthropods was not observed to lead to an increase
in herbivorous insect populations as a result of bluebirds
occupying songbird nest boxes.
Do avian insectivores target prey based on size, reducing
some size classes near nest boxes? Predaceous arthropods were
more likely to be large bodied and avian foraging reduced the
abundance of large arthropods, supporting the findings of other
studies (Philpott et al. 2004). Optimal foraging theory predicts
generalist birds are more likely to forage for larger, more
energetically favorable prey (Pyke et al. 1977). However, our
results show that during the peak intensity of the breeding
season, avian predators can reduce the abundance of small and
medium-bodied prey as well. It is notable that large arthropods
were two-thirds less abundant in the nest box treatment than
control area at the beginning of May, whilst abundances of
smaller arthropods such as leafhoppers, flea beetles, and aphids
were similar. These trends could be a result of early season
foraging by insectivorous birds as they are defending
territories, building nests, and laying eggs. There is a likely
trade-off between prey abundance and size, such that when
large taxa are not available, birds must forage for smaller, more
abundant prey.
The costs and benefits of enhancing bird diversity by
providing nest boxes will depend on site-specific factors such
as target pest species and size of available arthropod prey.
Nevertheless, our study shows that adding nest boxes to
vineyards can encourage songbirds to nest in agricultural
habitats and provide an ecosystem service in the form of pest
control.
ACKNOWLEDGEMENTS
We thank David Koball, Mary Fetzer and Bonterra/Fetzer
Vineyards for their cooperation and access to study sites. D.
Thayer and D. Smith at UCSC helped to construct nest boxes.
We thank the Hopland Research and Extension Center for
housing and services. Funding for this research was provided
by: The Organic Farming Research Foundation; Animal
Behavior Society; Wilson Ornithological Society; Annie’s
Sustainable Agriculture Graduate Scholarship; and the
Environmental Studies Department at University of California
Santa Cruz. Approval was granted for researching wild birds
by the United States Geological Survey (Permit Number:
22665) and the University of California’s Institutional Animal
Care and Use Committee (Permit Number:Letod0705).
J.A. Jedlicka, D.K. Letourneau & T.M. Cornelisse / Conservation Evidence (2014) 11, 34-38
38
ISSN 1758-2067
Conservation Evidence is an open access online journal devoted to publishing the evidence on the effectiveness of management interventions. The other papers
from Conservation Evidence are available from www.ConservationEvidence.com. The pdf is free to circulate or add to other websites and is licensed under the
Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/.
REFERENCES
Costello M.J. & Daane K.M. (2003) Spider and Leafhopper
(Erythroneura spp.) Response to Vineyard Ground Cover.
Environmental Entomology, 32, 10851098.
Feil H., Feil W.S. & Purcell A.H. (2003) Effects of date of
inoculation on the within-plant movement of Xylella
fastidiosa and persistence of Pierce’s disease within field
grapevines. Phytopathology, 93, 244251.
Glisan King A. & Meinwald, J. (1996) Review of the defensive
chemistry of coccinellids. Chemical Reviews, 96, 1105
1122.
Heaton E. & Merenlender A.M. (2000) Modeling vineyard
expansion, potential habitat fragmentation. California
Agriculture, 54, 1219.
Heaton E., Long R., Ingels C. & Hoffman T. (2008) Songbird,
bat, and owl boxes: Vineyard management with an eye
toward wildlife. (W. Tietje, editor). University of
California Agriculture and Natural Resources Publication
21636, Oakland.
Holmes R.T. (1990) Ecological and evolutionary impacts of
bird predation on forest insects: An overview. Studies in
Avian Biology, 13, 613.
Jedlicka J.A., Greenberg R. & Letourneau D.K. (2011) Avian
conservation practices strengthen ecosystem services in
California vineyards. PLoS ONE, 6, e27347.
Merenlender A.M. & Crawford J. (1998) Vineyards in an oak
landscape: Exploring the physical, biological, and social
benefits of maintaining and restoring native vegetation in
and around the vineyard. University of California
Agriculture and Natural Resources Publication 21577,
Oakland.
Mooney K.A., Gruner D.S., Barber N.A., Van Bael S.A.,
Philpott S.M. & Greenberg R. (2010) Interactions among
predators and the cascading effects of vertebrate
insectivores on arthropod communities and plants.
Proceedings of the National Academy of Sciences of the
United States of America, 107, 73357340.
North American Bluebird Society (2008) Eastern or Western
Bluebird nestbox.
http://www.nabluebirdsociety.org/eastwestbox.htm
(accessed 1 Nov 2007).
Osborne, K.H. & Allen W.W. (1999) Allen-Vac: An internal
collection bag retainer allows for snag-free arthropod
sampling in woody scrub. Environmental Entomology,
28, 594596.
Philpott S.M., Greenberg R., Bichier P. & Perfecto I. (2004)
Impacts of major predators on tropical agroforest
arthropods: comparisons within and across taxa.
Oecologia, 140, 140149.
Partners in Flight (2002) Version 2.0. The oak woodland bird
conservation plan: a strategy for protecting and managing
oak woodland habitats and associated birds in California
(S. Zack, lead author).
http://www.prbo.org/calpif/plans.html (accessed 16 Oct
2011).
Pyke G. H., Pulliam H.R. & Charnov E.L. (1977) Optimal
Foraging - Selective Review of Theory and Tests.
Quarterly Review of Biology, 52, 137154.
Toops C. 1994. Bluebirds Forever. Voyageur Press.
Triplehorn C.A. & Johnson N. F. (2005) Borror and DeLong’s
Introduction to the study of insects, 7th edition. Thomson
Brooks/Cole, Belmont, CA.
Van Bael S.A., Philpott S.M., Greenberg R., Bichier P., Barber
N.A., Mooney K.A. & Gruner D.S. (2008) Birds as
predators in tropical agroforestry systems. Ecology, 89,
928934.
... Farmland insectivorous birds can provide high value pest control services (Maas et al., 2016;Génard et al., 2017;García et al., 2018). Therefore, enhancing their breeding or site occupancy opportunities may strengthen crop pest regulation in diverse agroecosystems (Mols and Visser, 2007;Jedlicka et al., 2014;Rey Benayas et al., 2017;García et al., 2020;Díaz-Siefer et al., 2022). ...
... Sustainable solutions to pest management in agroecology are increasingly relying on natural pest control by a wide range of organisms including insectivorous birds (Sekercioglu, 2006;Wenny et al., 2011;Díaz-Siefer et al., 2022). Birds can contribute to 20-70 % reduction in arthropod biomass (Sekercioglu, 2006;Jedlicka et al., 2014;García et al., 2020), consume agricultural pests (Jedlicka et al., 2013;Karp et al., 2014), and lower pest damage to plants with subsequent higher crop yield or fruit production (Whelan et al., 2015). Further, there is evidence that predation pressure on apple pests can increase in orchards with nest boxes (García et al., 2020). ...
Article
Great tits are insectivorous birds that feed mainly on caterpillars during the breeding season. Their high pest control potential in apple orchards has been documented. Nestbox provisioning is an increasingly suggested tool for ecological pest control, but the underlying assumption that birds forage in intensively managed orchards has never been formally tested. We conducted a fine-scale study of the great tit feeding microhabitat in different orchard management contexts as pesticide use affects the behaviour and physiology of birds through direct intoxication and reduced prey abundance. Using radiotracking techniques, we assessed foraging areas and foraging habitat selection of female great tits breeding in conventional and organic commercial apple orchards. We also tested whether different orchard-driven foraging strategies could be linked to differences in reproductive success. We collected 392 foraging locations from seven female great tits nesting in organic orchards and 375 locations from seven females nesting in conventional orchards. Females from organic orchards mostly searched for food inside the orchard where they bred. This contrasted strongly with females from conventional orchards (54 ± 10.4 % and 7.1 ± 3.0 % of foraging points inside the orchard, respectively). Further, females from organic orchards travelled shorter distances. Overall, organic orchards and hedgerows were the most preferred foraging habitats. Conventional orchard management was also associated with lower nestling survival and lower fledgling number than organic management. There were indications that the mean number of fledglings decreased with increasing mean foraging distance of the female. Our novel insights on the foraging behaviour of great tits in orchards support the benefits of installing nestboxes in organic but not in conventional orchards. We posit that nestboxes may encourage feeding activity of insectivorous birds within organic orchards where they may then contribute to the control of insect pest populations.
... Wrens), suggesting nest boxes might be useful in helping farmers control insect pests. Indeed, nest boxes are commonly deployed in temperate agricultural systems to attract insectivorous birds and predatory raptors, which, in turn, can help control insect pests, (e.g., Benayas et al., 2017;Jedlicka et al., 2011Jedlicka et al., , 2014Olmos-Moya et al., 2022), rodents (e.g., Kross et al., 2016), and even pest birds (e.g., Shave et al., 2018). Prior work has shown that House Wrens rapidly occupy nest boxes in Chilean vineyards and feed on insects nearby, causing elevated predation rates on sentinel insect prey near boxes (Olmos-Moya et al., 2022). ...
Article
Full-text available
Most studies comparing biodiversity between natural and human‐modified landscapes focus on patterns in species occurrence or abundance, but do not consider how different habitat types meet species' breeding requirements. Organisms that use or nest in tree cavities may be especially threatened by habitat conversion due to the loss of their nesting sites. Although cavity‐nesting bird diversity is highest in the tropics, little is known about how tropical birds use cavities, how agriculture affects their reproductive biology, and how effective nest boxes could be as a conservation strategy in tropical agriculture. Here, we explored how habitat conversion from tropical forests to pasture affects the abundance, nesting habitat availability, and nest success of cavity‐nesting birds in Northwest Ecuador. We conducted bird surveys and measured natural cavity availability and use in forest and agriculture. We also added artificial nest boxes to forest and agriculture to see whether cavity limitation in agriculture would elicit higher use of artificial nest boxes. We found evidence of cavity limitation in agriculture—there were many more natural cavities in forest than in agriculture, as well as more avian use of nest boxes placed in agriculture as compared to forest. Our results suggest that it is important to retain remnant trees in tropical agriculture to provide critical nesting habitat for birds. In addition, adding nest boxes to tropical agricultural systems could be a good conservation strategy for certain species, including insectivores that could provide pest‐control services to farmers. Abstract in Spanish is available with online material.
... In agro ecosystem, insectivorous birds play vital role in controlling pest in fields. It was found that there was 20 to 70% reduction in biomass of invertebrates due to predation of birds in vineyards and other agroecosystem (Sekercioglu, 2006 [105,5,49] . They also reduce the number of herbivores which helps in decreasing the damage of leaf and mortality of plants and as a result there was 60% increase in [74,69,116] . ...
Article
Full-text available
Different types of ecosystem and ecological resources related to them signify their preponderance to mankind. Ecosystem maintains the balance between mankind and other organisms by exerting direct or indirect influence on environment. Birds are most crucial and inseparable components of the earth's ecosystem and play several roles like pollinators, seed dispersers, predators, scavengers etc. and contribute to all the four ecosystem services viz. provisioning, regulation, cultural and supporting services as defined by the United Nations Millennium Ecosystem Assessment. The global loss of avian population implies reduction in ecosystem services and hence affecting the human life. The contribution of birds in our economy and maintenance of sustainable ecosystem remains unaccountable due to lack of information on their ecological value and tangible benefits. The complete evaluation of all the services rendered by avian fauna helps us to understand their significance in ecosystem sustainability and crucial role they play in human's life. The outcomes of scientific study on crucial role of birds to sustain different types of ecosystem will help the public and policy makers to understand the consequences of diminution in bird's population and spreading awareness about their conservation.
... Birds are among the important and efficient arthropod predators in agroecosystems, with 50 percent feeding primarily on insects and 75 percent occasionally feeding on invertebrates [52]. Studies of predation on insect pests by birds in natural and agricultural areas have found that invertebrate reductions by birds range from 20 to 70 percent [53]. This predation by birds not only reduces the number and incidence of herbivores but also significantly reduces foliar damage and plant mortality and can result in up to a 60 percent increase in crop yield or fruit production [52]. ...
Article
Full-text available
Birds play many roles, including predators, pollinators, scavengers, seed dispersers, pests, predators, nutrient cycling, ecosystem engineers, and many other services. However, the global decline in bird populations means that the ecosystem services provided by these birds are also declining [1]. The services birds provide are ecologically and economically important, but are not adequately appreciated due to insufficient information. Therefore, this review article aims to elucidate the role of birds in the agro-ecosystem and their benefits to humans in order to promote their conservation. Healthy bird populations and their habitats would help protect various ecological services that would ultimately improve human well-being.
... These variables generally correlate with reproductive success and nestling weight, suggesting an absence of ecological traps in the habitats examined here. This is an encouraging finding, validating ongoing efforts to bolster cavity-nesting bird populations in anthropogenic systems, for the benefit of humans (e.g., insect pest control; Jedlicka et al., 2011Jedlicka et al., , 2014Shave et al., 2018) and the birds themselves (Dybala et al., 2018;Finch et al., 2019;Norris et al., 2018). ...
Article
Full-text available
Long-term studies on the impacts of global change on reproduction are rare, even though reproductive output can respond more quickly than species' abundances or distributions. We explore the influences of habitat use and weather on fitness, by using an 11-year dataset of 2305 nesting attempts (7174 nestlings) across four species of cavity-nesting songbirds within California's Central Valley. Specifically, we modeled relationships between habitat type, maximum nesting season temperature, and winter/nesting season precipitation and nest site selection, reproductive success, and nestling weight for each species. We found that species selected nest sites based on species-specific habitat variables and that reproductive success and nestling weight peaked in selected habitats, suggesting an absence of ecological traps. Higher maximum nesting season temperatures were negatively associated with clutch size, reproductive success, and nestling weight for all species. For example, models predicted that the probability of successfully fledging tree swallows declined by 39 % and tree swallow nestling weight declined by 19 % when nests experienced the hottest versus the coolest maximum temperatures. In contrast, the effects of precipitation on reproductive outcomes varied by species and timing. We observed strong negative associations between nesting season precipitation and reproductive success/nestling weight in tree swallows and western bluebirds. Our findings suggest that, while habitat conversion to orchards has not resulted in ecological traps, predicted increases in temperature and spring precipitation may reduce the fitness of cavity-nesting songbirds in California. More broadly, our results highlight the importance of long-term monitoring when unravelling impacts of global change on fitness.
... Such enhancements attract beneficial birds to specific places in the landscape (e.g., crop fields), and so can facilitate the delivery of ecosystem services. For example, installing boxes for Western Bluebirds (Sialia mexicana) in California, USA, vineyards decreased abundance of a sentinel prey arthropod pest (Jedlicka et al. 2014), and using nest boxes to attract Great Tits (Parus major) to apple orchards in the Netherlands resulted in less fruit damage by caterpillars (Mols and Visser 2007). ...
Article
Full-text available
Landscape enhancements such as nest boxes can attract birds to agricultural areas, where they can provide ecosystem services such as pest reduction through their consumption of crop pests. However, there are large gaps in knowledge about how birds respond to enhancements. From 2014 to 2018 we installed American Kestrel (Falco sparverius; hereafter kestrel) nest boxes in a blueberry production region in western Michigan. From 2015 to 2018 we conducted surveys to monitor kestrel presence along 1.6-km transect segments (hereafter, sites) to estimate kestrel occupancy in areas with and without boxes. We also monitored box occupancy and reproductive success. Kestrel presence increased over time in the study area although there was some uncertainty in this trend. The presence of a box at a site did not increase kestrel presence there, but boxes in neighboring sites did increase presence. This indicated that enriching an area with boxes increases kestrel presence. Box occupancy rates were positively influenced by occupancy of the same box the previous year. Percent successful nests ranged from 75 to 100 percent, and mean number of fledglings produced was approximately 4 per nest box. Our results showed that nest boxes can serve as effective landscape enhancements to attract kestrels to agricultural landscapes, but the degree to which kestrels occupy boxes can vary geographically. Local-scale studies can provide information about the potential benefits and challenges of using nest boxes as a pest management tool.
... Nevertheless, it should be worth testing general measures that have already proved positive for biodiversity in olive orchards, such as retaining herbaceous cover and woody hedges (Castro-Caro et al., 2015;Rey et al., 2019), but also in other agricultural systems, such as retaining woodland and shrubland patches, including isolated large trees (e.g. Manning et al., 2006;Tryjanowski et al., 2011;Morelli, 2013), or the provisioning of nest boxes (Jedlicka et al., 2014). The implementation of such measures might be supported by agri-environment schemes, at it is the case already for the maintenance of herbaceous cover (see for e.g. ...
Thesis
Full-text available
Biodiversity is a global asset of significant value to present and future generations. Yet, driven by the fast human population growth and associated increases in resource use since mainly the 1950s, biodiversity is now facing a major global decline. The causes of this decline are varied, but the expansion and intensification of agricultural production and animal rearing are among the primary drivers in many regions of the world. Reverting the decline is therefore dependent on policies and management solutions that reconcile agricultural production with environmental sustainability and biodiversity conservation. This thesis addresses these issues, by investigating the drivers, land-use dynamics and biodiversity effects of olive farming intensification, a widespread agricultural system across the biodiversity-rich Mediterranean region, where it is fast expanding and intensifying. We show that a fast expansion of intensive olive orchards occurred during the last three decades in Southern Portugal, mostly replacing dry annual crops (63%) and rainfed olive groves (21%), with the availability of irrigation water in large farms strongly favouring these transitions. We also show that this process strongly affects breeding and wintering bird communities, with particularly negative effects demonstrated for open farmland bird species of conservation concern, and for cavity-nester insectivores breeding within olive orchards. However, we also found potentially positive effects on frugivorous wintering bird communities, due to increased olive availability in the more intensive orchards. Taken together, our results provide important baseline information that can help predict how future agricultural and environmental policies, as well as fluctuations in global olive oil markets, can affect Mediterranean land cover change and local biodiversity. They also support the design of management guidelines for preserving biodiversity in Mediterranean olive farming landscapes, suggesting that these should consider not only the environmental impacts and risks of the intensification process, but also some potential conservation opportunities.
... Birds are efficient arthropod predators in farmland, where 50% are predominantly feeding on insects, and 75% consume invertebrates at least occasionally [18,22]. Avian predation on insects' pests has been studied in various natural and agricultural systems where most studies report a marked reduction in invertebrates' biomass by birds, usually ranging from 20% to 70% [17,23,24]. This predation not only lowers herbivorous abundance but also significantly reduces leaf damage and plant mortality, potentially leading to up to 60% increase in crop yield or fruit production [25,22]. ...
... On the other hand, the beating sampling evidenced that the use of nest boxes decreased arthropod biomass on apple trees. This latter result might seem in conflict with the similar number of individuals of arthropods found in nest box and control orchards, but may well suggest that birds exert a stronger pressure on large preys than on small ones (Jedlicka et al., 2014). Nevertheless, occupied nest boxes significantly reduced the probability of occurrence of pests on apple trees (see also Mols & Visser, 2007). ...
Article
1. Ecological intensification in croplands aims to enhance biodiversity‐based ecosystem services, helping to increase yield while reducing agricultural environmental impacts. Identifying ecological intensification tools of wide applicability and easily implemented by farmers is, therefore, an imperative. Here, we verify the efficiency of provisioning artificial nest boxes for insectivorous birds to reinforce pest biological control in apple orchards. 2. The study was conducted in 24 cider‐apple orchards in Asturias (NW Spain) over three years. We compared the effect of insectivorous birds between orchards with and without nest boxes occupied by different bird species, through insectivory estimates based on attack on a sentinel pest and measurements of arthropod abundance in apple trees. We also identified preys that birds of different species captured to feed nestlings. 3. Bird occupancy of nest boxes was widespread, ranging 25.0‐33.3% each year. Great tit was the dominant species, followed by blue tit and, occasionally, common redstart. 4. Predation pressure on apple pests increased in orchards with nest boxes, as judged by the increased proportion of sentinel models attacked by birds (34.9% increase in 2018 and 41.1% in 2019), decreased biomass of tree‐dwelling arthropods (‐51.7%) and reduced probability of apple pest occurrence (from 57 to 40%), compared to orchards without nest boxes. 5. Nesting species showed different predatory roles in apple orchards. Fewer attacks on sentinel pests but lower arthropod biomass was associated with blue tit rather than great tit. Besides, blue tit fed nestlings at a faster rate and included in their diet a higher proportion of apple pests than great tit, which preyed mostly on other herbivorous insects. 6. Synthesis and applications. We demonstrated the usefulness of nest boxes for insectivorous birds in enhancing biological control of apple pests at a regional scale, identifying tit species as complementary predators of apple pests and herbivores. From the farmers’ perspective, providing nest boxes in orchards may represent an efficient, easy to implement, cheap and attractive measure of ecological intensification, compatible with other actions fostering biodiversity in croplands.
Article
Full-text available
We used a statistical modeling technique called logistic regression analysis, and a geographic information system (GIS), to map areas of possible future vineyard expansion in Sonoma County, based on data about vineyard development from 1990 through 1997. The goal of this research was to develop a model that would improve our understanding of vineyard expansion patterns at a landscape scale (for instance, including an entire county). The approach involved identifying landscape characteristics that were associated with vineyard development and mapping the areas with similar characteristics that were undeveloped in 1997. We used the results to map where habitat removal and fragmentation could result from vineyard expansion. This method, although still under development, is designed for county- or regional-scale analysis to assist land-use planners, natural resource protection agencies and land conservation programs in protecting valuable environmental resources while sustaining a vital agricultural economy.
Article
Full-text available
Insectivorous Western Bluebirds (Sialia mexicana) occupy vineyard nest boxes established by California winegrape growers who want to encourage avian conservation. Experimentally, the provision of available nest sites serves as an alternative to exclosure methods for isolating the potential ecosystem services provided by foraging birds. We compared the abundance and species richness of avian foragers and removal rates of sentinel prey in treatments with songbird nest boxes and controls without nest boxes. The average species richness of avian insectivores increased by over 50 percent compared to controls. Insectivorous bird density nearly quadrupled, primarily due to a tenfold increase in Western Bluebird abundance. In contrast, there was no significant difference in the abundance of omnivorous or granivorous bird species some of which opportunistically forage on grapes. In a sentinel prey experiment, 2.4 times more live beet armyworms (Spodoptera exigua) were removed in the nest box treatment than in the control. As an estimate of the maximum foraging services provided by insectivorous birds, we found that larval removal rates measured immediately below occupied boxes averaged 3.5 times greater than in the control. Consequently the presence of Western Bluebirds in vineyard nest boxes strengthened ecosystem services to winegrape growers, illustrating a benefit of agroecological conservation practices. Predator addition and sentinel prey experiments lack some disadvantages of predator exclusion experiments and were robust methodologies for detecting ecosystem services.
Article
Full-text available
Ground cover is used in some vineyards to improve soil structure and help manage insect pests; previous studies have shown lower leafhopper (Erythroneura spp.) densities on vines grown with ground cover. We undertook a 2-yr study to determine why ground cover is associated with reduced leafhopper densities. Ground cover consisted of a fall-planted cover crop of purple vetch (Vicia benghalensis) and barley (Hordeum vulgare), which senesced in May and was replaced by a complex of resident vegetation comprised primarily of the grasses Echinochloa spp., Digitaria sanguinalis, and Setaria spp., as well as common knotweed (Polygonum aviculare). We compared three treatments during the growing season: Cover, No Cover, and Cover/Exclusion. Cover/Exclusion was similar to Cover treatment but with barriers to impede arthropod movement between ground cover and vines. We measured leafhopper density and egg parasitism, spider density and diversity, and grapevine vigor, and found that mid- and late-season leafhopper densities were significantly lower in Cover versus No Cover. Neither leafhopper egg parasitism nor spider density on the vines or ground cover could explain these differences; however, grapevine vigor was significantly lower in Cover than No Cover, and provides the best correlation to leafhopper density. Late-season leafhopper density was highest in the Exclusion treatment but cannot be explained by changes in grapevine vigor. Individual spider species composition and density on the grapevine canopy varied significantly among treatments: Trachelas pacificus (Chamberlin and Ivie) was higher in the Cover treatment, Hololena nedra Chamberlin and Ivie, Cheiracanthium inclusum (Hentz), and Neoscona oaxacensis (Keyserling) were lower in the Exclusion treatment, and Oxyopes spp. was higher in the Exclusion treatment. We suggest the lower densities of leafhoppers in the Cover treatment resulted from poorer host plant quality because of the competition between ground cover and grapevines. The higher late-season leafhopper densities in the Exclusion treatment may be due to changes in spider species composition, and subsequently, differences in rates of predation on leafhopper nymphs.
Article
Full-text available
Theory on trophic interactions predicts that predators increase plant biomass by feeding on herbivores, an indirect interaction called a trophic cascade. Theory also predicts that predators feeding on predators, or intraguild predation, will weaken trophic cascades. Although past syntheses have confirmed cascading effects of terrestrial arthropod predators, we lack a comprehensive analysis for vertebrate insectivores-which by virtue of their body size and feeding habits are often top predators in these systems-and of how intraguild predation mediates trophic cascade strength. We report here on a meta-analysis of 113 experiments documenting the effects of insectivorous birds, bats, or lizards on predaceous arthropods, herbivorous arthropods, and plants. Although vertebrate insectivores fed as intraguild predators, strongly reducing predaceous arthropods (38%), they nevertheless suppressed herbivores (39%), indirectly reduced plant damage (40%), and increased plant biomass (14%). Furthermore, effects of vertebrate insectivores on predatory and herbivorous arthropods were positively correlated. Effects were strongest on arthropods and plants in communities with abundant predaceous arthropods and strong intraguild predation, but weak in communities depauperate in arthropod predators and intraguild predation. The naturally occurring ratio of arthropod predators relative to herbivores varied tremendously among the studied communities, and the skew to predators increased with site primary productivity and in trees relative to shrubs. Although intraguild predation among arthropod predators has been shown to weaken herbivore suppression, we find this paradigm does not extend to vertebrate insectivores in these communities. Instead, vertebrate intraguild preda-tion is associated with strengthened trophic cascades, and insectivores function as dominant predators in terrestrial plant-arthropod communities.
Article
Full-text available
Science Citation Classic Award Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by menas of mathematical models. These models are very similar, in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) - usually energy - and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e. optimal diet); (2) choice of which patch type to feed in (i.e. optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test such predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will require much modification, especially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated than just energy.
Article
Allen-vac, a gardeners' blower-vacuum modified for arthropod sampling, has a unique, completely internal collection bag retainer that allows snag-free sampling from dense woody scrub habitats such as coastal sage, chaparral, and thorn scrub as well as agricultural conditions. This vacuum machine modification is described.