Birds caught in spider webs in Asia

Abstract

A recent global review of birds caught in spider webs reported only three Asian cases. Given this surprisingly low number, I made a concerted effort to obtain additional Asian cases from the literature, the internet, and field workers. I present a total of 56 Asian cases which pertain to 33 bird species. As in the global dataset, mostly small bird species were caught in spider webs, with a mean body mass of 17.5 g and a mean wing chord length of 73.1 mm. Consequently, birds with a body mass >30 g were very rarely caught. This Asian review corroborates the global review that smaller birds are more likely to be caught and that Nephila spiders are most likely to be the predators. Continuous monitoring of spider webs is recommended to ascertain the frequency of these events.

Full text

Walther Avian Res (2016) 7:16
DOI 10.1186/s40657-016-0051-4
SHORT REPORT
Birds caught inspider webs inAsia
Bruno A. Walther*
Abstract
A recent global review of birds caught in spider webs reported only three Asian cases. Given this surprisingly low
number, I made a concerted effort to obtain additional Asian cases from the literature, the internet, and field workers.
I present a total of 56 Asian cases which pertain to 33 bird species. As in the global dataset, mostly small bird species
were caught in spider webs, with a mean body mass of 17.5 g and a mean wing chord length of 73.1 mm. Conse‑
quently, birds with a body mass >30 g were very rarely caught. This Asian review corroborates the global review that
smaller birds are more likely to be caught and that Nephila spiders are most likely to be the predators. Continuous
monitoring of spider webs is recommended to ascertain the frequency of these events.
Keywords: Spider, Predator–prey relationships, Asia
© 2016 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License
(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,
provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/
publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Background
Birds may be killed by environmental factors (e.g.
weather; Elkins 2004), accidents or parasites (e.g. Jen-
nings 1961), or predators. e most important preda-
tors of birds are birds, reptiles and mammals, including
humans, but, more rarely, birds are also predated upon
by amphibians, fish and insects (Brooks 2012). A presum-
ably rather rare case of death occurs when a bird gets
caught in a spider web; in a global review, Brooks (2012)
reviewed 68 cases of birds getting trapped and often
killed in the webs of large spiders. When a bird flies into a
spider web, the bird may either bounce off the web or fly
right through it, or it may become entangled; once entan-
gled, the spider may or may not wrap the bird in silk.
Entangled birds may then free themselves again, or they
die either due to exhaustion or spider predation, while
wrapped birds invariably die unless freed by humans (for
details, see Brooks 2012).
Birds should therefore always attempt to avoid colli-
sion with spider webs, while the interests of spiders may
differ depending on the species. Some spider species
opportunistically consume trapped birds (especially large
Nephila spiders, see below) and may therefore keep their
webs inconspicuous to birds. However, other spider spe-
cies apparently try to avoid collisions and the consequent
damage to their webs by making them more visible to
birds (Bruce etal. 2005; Walter and Elgar 2011).
As one may expect, Brooks’ (2012) global review docu-
mented that it is almost exclusively smaller birds (mean
body mass=10.7g, mean wing chord length=61mm)
which get caught in spider webs. Consequently, 88 and
90% of all caught birds had a body mass ≤15g and a
wing chord length <90mm, respectively. In the 34 cases
in which the spider was identified, 62% belonged to the
genus Nephila, and all were orb weavers except for a sin-
gle Latrodectus species.
Most of these cases were reported from Africa, Aus-
tralia, North America, and the Neotropics, but only a
few from Europe and Asia (D. Brooks in litt. 2014). us,
Brooks (2012) only reported three Asian cases: a Spotted
Flycatcher (Muscicapa striata) in Iran (Doberski 1973),
a juvenile Laughing Dove (Streptopelia senegalensis) in
Oman in 2003 (Forsman 2003), and a Dusky Warbler
(Phylloscopus fuscatus) in China some time before 2007
(D. Brooks in litt. 2014). Kasambe etal. (2010) presented
another four cases from India not mentioned in Brooks
(2012). Given that Nephila species are distributed across
much of tropical, subtropical and even some parts of tem-
perate Asia (Miyashita etal. 1998; Murphy and Murphy
2000; Lee etal. 2004; Harvey etal. 2007; Su etal. 2007,
2011; http://www.gbif.org/species/2149490), this relative
lack of records seemed surprising. erefore, I made a
concerted effort to obtain additional cases of birds being
caught in spider webs in Asia using various sources.
Open Access
Avian Research
*Correspondence: spidercatchbird@gmail.com
Master Program in Global Health and Development, College of Public
Health, Taipei Medical University, 250 Wu‑Hsing St., Taipei 110, Taiwan,
China

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Walther Avian Res (2016) 7:16
Methods
In 2014 and early 2015, I used eight methods to obtain
additional cases from the literature, the internet, Asian
ornithologists, birdwatchers and birding tour leaders:
(1) I emailed all the authors who published in Birding-
ASIA and Forktail and whose emails I could take from
the journals’ websites or the Web of Science. (2) I emailed
all the authors of any article published in an ornitho-
logical journal listed on the Web of Science which were
returned upon using the keywords “bird” and “Asia”. (3) I
posted requests on the birding fora of the Birds of Banga-
lore, Birds of Bombay, Bombay Natural History Society,
Hong Kong Bird Watching Society, Hong Kong Wildlife
Net, Kerala Birder, Malaysia Birders, Oriental Bird Club,
Ornithological Society of the Middle East, and Pengamat
Burung Indonesia. (4) I extensively used the web, images
and video search functions of Google and Google Scholar
using various combinations of the keywords “spider”
“catch” “bird” “Asia” and names of Asian countries. (5)
Upon any reply, I asked the person to forward my email
request to other Asian ornithologists and birdwatchers.
(6) I tried to obtain all references given in publications or
websites which reported another case. (7) In early 2014,
two native Chinese speakers (J.-L. Wu, T.-Y. Wu in litt.
2014) used Google Taiwan to search Taiwanese web-
sites for cases using relevant keywords (see above), and
I emailed all Taiwanese ornithologists and birders that
I personally knew. (8) In late 2014, two native Japanese
speakers (M. Kamioki, M. Mashiko in litt. 2014) used
Google Japan to search Japanese websites for cases using
relevant keywords (see above). I kindly request that fur-
ther cases be reported to my email.
For easy comparison, I mirrored Brooks’ (2012) analy-
sis as much as possible. As described in Brooks (2012), I
sought data on body mass and wing chord length for each
bird species from various data sources (given in Table1)
and, if possible, determined the species of spider (given
in Table1). Unlike Brooks (2012), I added location and
date for each record, if possible.
Results
In Asia, I was able to document 53 cases in addition to
the three cases listed by Brooks (2012) (Table 1). e
Asian cases now contain 33 bird species, and together
with Brooks’ (2012) global dataset, 84 bird species have
been documented so far (Table2). ree and 12 spider
species were identified for Asia and the world, respec-
tively; these are (with the number of Asian cases and
cases from other continents in brackets): Aranens trifo-
lium (0/1), Argiope aurantia (0/3), Argiope caphinarium
(0/1), Argiope sp. (0/2), Eriophora biapicata (0/1), Latro-
dectes sp. (0/1), Mastophora sp. (0/1), Neoscona hentzii
(0/1), Nephila antipodiana (3/3), Nephila clavipes (0/14),
Nephila pilipes (31/32), Nephila sp. (4/8), Nephilengys
cruentata (0/2), Poecilotheria fasciata (1/1), and uniden-
tified spiders (17/49) [Brooks (2012) also mentions Neph-
ila inaurata in his text, but it is not listed in his Table1].
us, 38 out of 39 identified cases (97 %) in Asia were
Nephila species.
e mean body mass and mean wing chord length
are slightly larger for the Asian than for the global data-
set (Table 2). is difference is certainly due to the
large number of hummingbirds in Brooks’ (2012) data-
set which are all smaller than the smallest Asian spe-
cies, the Greenish Warbler (Phylloscopus trochiloides;
Table1). Means are also slightly larger for the means cal-
culated across all species than for the means calculated
across all individual cases (Table 2). is difference is
due to smaller-than-average species caught repeatedly;
of the 14 species with more than one case, 11 species
had a body mass ≤10g and 9 species had a wing chord
length ≤60mm (Table1; Brooks 2012). Among the 49
Asian cases identified to bird species, 71 and 88% of all
caught birds had a body mass ≤15g and a wing chord
length <90mm, respectively; for the 114 global cases, the
respective percentages are 82 and 89% (Table1; Brooks
2012). A frequency diagram of all cases shows the great
propensity of small-bodied birds being caught (Fig. 1).
Cases with a body mass >30g are exceedingly rare, and
the two largest species ever caught, the Laughing Dove
(80.0 g) and the Brown-eared Bulbul (Ixos amaurotis,
70.9g), are anomalies in the general trend.
e oldest case recorded in Asia is the Dusky Crag
Martin (Hirundo concolor) reported in Morris (1889)
that equals the previous oldest record by McCook (1889)
cited in Brooks (2012). Only 11 of the Asian cases are
from before 2000 (Table1); likely reasons are that many
records were reported on the internet (Table1), and that
many of the contacted ornithologists and birdwatchers
were not active before 2000.
Discussion
Birds are usually predators of spiders or the contents
of their webs (e.g. Waide and Hailman 1977; Gunnars-
son 2007), but when small birds encounter spider webs
of large spiders, the tables can be turned. Overall, this
review of Asian cases corroborates the conclusions made
by Brooks (2012), namely: (1) the smaller the bird species,
the higher the likelihood to be caught in spider webs; and
(2) Nephila species are by far the most common spiders
to catch birds in their webs.
However, my review of Asian cases suggests that cases
of birds getting caught in spider webs may be as common
in Asia as in other continents wherever large orb weaver
spiders are common. erefore, the small number of
Asian cases in Brooks (2012) represented a biased picture

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Walther Avian Res (2016) 7:16
Table 1 Birds entrapped inspider webs inAsia andtheir respective sizes
Common name Scientic name Spider sp. Mass (g) Wing (mm) Location Date Source
Glossy Swiftlet Collocalia esculenta Np 8.0 950,2,3 Great Nicobar island,
Nicobar Islands,
India
Before 2010 Manchi and Sankaran
(2009)
Edible‑nest Swiftlet Collocalia fuciphaga S 10.7 1181,1,3 Interview Island,
Andaman Islands,
India
June 2006 Manchi and Sankaran
(2009)
Asian Palm Swift Cypsiurus balasiensis Na 9.2 1121,1,0 Doi Kham, Chiang
Mai Province,
Thailand
6 October 2014 W. Limparungpat‑
thanakij in litt. 2014
Laughing Dove Streptopelia senega-
lensis
Na 80.0c138cOman ~ October 2003 Forsman (2003),
Brooks (2012), D.
Brooks in litt. 2014
Pied Fantail Rhipidura javanica S 12.5 821,1,0 Near U Minh Thuong
National Park, Kien
Giang Province,
Vietnam
9 August 2008 M. Le in litt. 2014
Black‑naped Mon‑
arch Hypothymis azurea Np 11.3 69 Sanjay Gandhi
National Park,
Mumbai, India
October 1996 Andheria (1998, 1999)
Spotted Flycatcher Muscicapa striata S 14.0c80cMain Kaleh Reserve,
Iran 1972 Doberski (1973)
Grey‑streaked
Flycatcher Muscicapa griseis-
ticta
S 15.1 83 Taiwan Area September 2008 http://tinyurl.com/
spider‑tw2
Grey‑streaked
Flycatcher Muscicapa griseis-
ticta
Np 15.1 833,5,8 Iriomote Island,
Japan 5 October 2008 http://tinyurl.com/
spider‑jp6
Asian Brown Fly‑
catcher Muscicapa dauurica S 9.9 661,1,0 Thap Lan National
Park, Nakhon
Ratchhasima Prov‑
ince, Thailand
14 November 1999 P. Round in litt. 2014
Asian Brown Fly‑
catcher Muscicapa dauurica S 9.9 661,1,0 Po Toi Island, Hong
Kong, China After 2006 G. Welch in litt. 2014
Asian Brown Fly‑
catcher Muscicapa dauurica Np 9.9 661,1,0 Po Toi Island, Hong
Kong, China 8 September 2011 M. Hale and G. Welch
in litt. 2014
Hill Blue Flycatcher Cyornis banyumas Np 14.5 671,1,0 Bukit Larut, Perak
State, Malaysia Unknown Anonymous (1999b)
Great TitaParus major Np 15.5 591,0,0 Komesu, Itoman City,
Okinawa Island,
Japan
10 August 2011 http://tinyurl.com/
spider‑jp1, http://
tinyurl.com/spider‑
jp2
Dusky Crag MartinbHirundo concolor Pf 13.0 981,1,0 Shevaroys (=Ser‑
varayan) Hills near
Salem, Tamil Nadu
Before 1889 Morris (1889) and
Anonymous (1999a)
Light‑vented Bulbul Pycnonotus sinensis Np 29.7 85 Majia, Pingtung,
Taiwan Area March 2004 http://tinyurl.com/
spider‑tw3
Styan’s Bulbul Pycnonotus taivanus Np 26.2 84 Guangfu, Hualien,
Taiwan Area 18 June 2010 http://tinyurl.com/
spider‑tw4
Yellow‑vented
Bulbul Pycnonotus goiavier Np 27.8 821,4,6 Kledang‑Sayong For‑
est Reserve, Ipoh,
Perak, Malaysia
11 February 2014 Amar‑Singh (2014a,
b), Amar‑Singh H. in
litt. 2014
Buff‑vented Bulbul Iole olivacea S 24.5 891,1,0 Near Ban Bang
Khram, Khlong
Thom District,
Krabi (area also
known as Khao
Nor Chuchi),
Thailand
7 August 2013 P. Round in litt. 2014
Brown‑eared Bulbul Ixos amaurotis Np 70.9 1161,1,0 Tokunoshima Island,
Japan 1 August 2010 http://tinyurl.com/
spider‑jp3

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Walther Avian Res (2016) 7:16
Table 1 continued
Common name Scientic name Spider sp. Mass (g) Wing (mm) Location Date Source
Plain Prinia Prinia inornata Np 8.2 49 Tadoba Andhari
Tiger Reserve,
Chandrapur dis‑
trict, Maharashtra,
India
October 1998 Anonymous ( 1999a)
Plain Prinia Prinia inornata Np 8.2 49 Melghat Tiger
Reserve, northern
part of Amravati
District of Maha‑
rashtra State, India
Before 2005 Pande et al. (2004)
Plain Prinia Prinia inornata S 8.2 49 Western Ghats,
Maharashtra, India Unknown S. Pande in litt. 2015
Plain Prinia Prinia inornata S 8.2 49 Taiwan Area September 2008 http://tinyurl.com/
spider‑tw2
Oriental White‑eye Zosterops palpe-
brosus
Na 8.6 511,1,5 Sungei Buloh
Wetland Reserve,
Singapore
30 April 2012 Ong (2012a, b)
Japanese White‑eye Zosterops japonicus Np 11.3 53 Mong Tseng Tsuen
(near Tsim Bei Tsui),
Hong Kong, China
22 August 2004 So (2005)
Japanese White‑eye Zosterops japonicus Np 11.3 53 Keelung, Taiwan
Area 18 August 2005 http://tinyurl.com/
spider‑tw5
Japanese White‑eye Zosterops japonicus Np 11.3 53 Taiwan Area Before October 2005 http://tinyurl.com/
spider‑tw7
Japanese White‑eye Zosterops japonicus Np 11.3 53 Badouzi, Keelung,
Taiwan Island 13 August 2011 http://tinyurl.com/
spider‑tw6
Japanese White‑eye Zosterops japonicus Np 11.3 53 Okinawa Island,
Japan November 2012 http://tinyurl.com/
spider‑jp5
Lanceolated Warbler Locustella lanceolata S 12.9 55 E‑Luan‑Pi lighthouse,
Kenting National
Park, Pintung
County, Taiwan
Area
14 October 1984 TESRI# collection
number w672, C.‑t.
Yao in litt. 2013
Grasshopper Warbler Locustella naevia N 14.8 64 Tungareshwar
Wildlife Sanctuary,
Maharashtra, India
18 November 2006 Kasambe et al. (2010)
Common Tailorbird Or thotomus sutorius N 7.5 432,2,5 Mogarkasa Forest,
Nagpur, Maharash‑
tra, India
13 November 2008 Kasambe et al. (2010)
Dark‑necked Tai‑
lorbird Orthotomus atrogu-
laris
Np 7.7 381,1,0 Kaeng Krachan
National Park,
Petchaburi Prov‑
ince, Thailand
2012 W. Limparungpat‑
thanakij in litt. 2014
Dusky Warbler Phylloscopus fuscatus S 11.0c57cBeidahe, Hebei
Province, China Before 2007 D. Zetterström in litt.
2007 (D. Brooks in
litt. 2014)
Arctic Warbler Phylloscopus borealis Np 10.0 65 Yonaguni Island,
Japan 10 September 2008 http://ameblo.jp/
attacus/theme2‑
10004405518.html
Arctic Warbler Phylloscopus borealis Np 10.0 65 Bitou Cape, New Tai‑
pei City municipal‑
ity, Taiwan Area
6 September 2011 Y.‑P. Chiang in litt.
2013‒2014
Arctic Warbler Phylloscopus borealis Np 10.0 65 Pak Sha O, Hong
Kong, China 19 September 2015 Geoff Carey in litt.
2015
Greenish Warbler Phylloscopus tro-
chiloides
N 7.1 60 Bandhavgarh
National Park,
Madhya Pradesh,
India
12 October 2007 Kasambe et al. (2010)

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Walther Avian Res (2016) 7:16
Table 1 continued
Common name Scientic name Spider sp. Mass (g) Wing (mm) Location Date Source
Greenish Warbler Phylloscopus tro-
chiloides
N 7.1 60 Kanha National Park,
Madhya Pradesh,
India
22 October 2008 Kasambe et al. (2010)
Buff‑breasted Bab‑
bler Pellorneum tickelli S 17.1 611,1,0 Fraser’s Hill, Pahang,
Malaysia 5–11 June 2010 S. Pieterse in litt. 2014
Taiwan Yuhina Yuhina brunneiceps S 12.2 62 Taiwan Area Unknown H.‑S. Lin in litt. 2013
Vinous‑throated
Parrotbill Paradoxornis web-
bianus
Np 9.3 52 Mountain Pinglin,
Taichung City, Taip‑
ing District, Taiwan
Area
2007 http://tinyurl.com/
spider‑tw1
Brown‑throated
Sunbird Anthreptes mala-
censis
S 11.4 661,1,3 Ipoh City, Perak,
Malaysia 28 December 2007 Amar‑Singh (2014a,
b), Amar‑Singh H. in
litt. 2014
Eurasian Tree Spar‑
row Passer montanus S 23.0 66 Luku, Nantao
County, Taiwan
Area
1990s C.‑t. Yao in litt. 2013
Eurasian Tree Spar‑
row Passer montanus Np 23.0 66 Taiwan Area Summer 2004 http://tinyurl.com/
spider‑tw9
Eurasian Tree Spar‑
row Passer montanus S 23.0 66 Taiwan Area Before August 2010 http://tinyurl.com/
spider‑tw8
Eurasian Tree Spar‑
row Passer montanus Np 23.0 66 Jiji, Nantou County,
Taiwan Area 13 August 2013 C.‑t. Yao in litt. 2013
White‑rumped
Munia Lonchura striata S 11.3 48 Taiwan Area Unknown Y.‑C. Hsu in litt. 2013
Munia spec. – Np – – Bogor Botanical
garden, Bogor,
Indonesia
Before 1934 Boedijn (1933)
Munia spec. – Np – – probably near or in
Bogor, Indonesia Before 1934 Boedijn (1933)
“Small birds” – Np – – Thailand Before 1933 Bristowe (1932)
Unidentified – Np – – probably near or in
Bogor, Indonesia Before 1934 Boedijn (1933)
Unidentified – Np – – Cheung Sha, Lantau
Island, Hong Kong,
China
8 October 2006 Anonymous (2006)
Unidentified – Np – – Wang Tong River,
Mui Wo, Lantau
Island, Hong Kong,
China
12 October 2009 M. Pearse in litt. 2015
Unidentified – Np – – Miyakojima Island,
Japan 16 October 2011 http://tinyurl.com/
spider‑jp7
Common and scientic bird names and taxonomic order follow Inskipp etal. (1996)
Spider species as follows: S=bird was caught by a spider; N=bird was caught by a Nephila species, family Nephilidae, suborder Araneomorphae, order Araneae;
Na=bird was caught by Nephila antipodiana; Np=bird was caught by Nephila pilipes (=maculata); Pf=bird was caught by Poecilotheria (=Mygale) fasciata, family
Theraphosidae, suborder Mygalomorphae, order Araneae. Body masses were obtained from Glutz von Blotzheim (1966–1996), Dunning (2008), Severinghaus
etal. (2010), the Encyclopedia of Life (eol.org) and Wikipedia (en.wikipedia.org). Wing chord lengths were obtained from Glutz von Blotzheim (1966‒1996) and
Severinghaus etal. (2010) except when a superscript indicates the number of male, female and unsexed specimens which were measured by P. Capainolo (in litt.
2014) at the American Museum of Natural History, New Yor k, USA, H. van Grouw (in litt. 2014) at the Natural History Museum, Tring, UK, A. Gamauf (in litt. 2014) at the
Naturhistorische Museum Wien, Austria, and T. Töpfer (in litt. 2014) at the Zoologisches Forschungsmuseum Alexander Koenig, Bonn, Germany
a Also classied as Eastern Great Tit (Parus minor)
b The martin referred to in Morris (1889) must be a Dusky Crag Martin because of the record’s location and the use of a house to build its nest (R. Kasambe, H. Rathore,
in litt. 2014)
c I used the body masses and wing chord lengths given for the three Asian cases mentioned in Brooks (2012)
d TESRI refers to Taiwan Endemic Species Research Institute, Jiji, Nantou County, Taiwan Area

Page 6 of 7
Walther Avian Res (2016) 7:16
of the Asian situation. Asia covers 30% of the world’s ter-
restrial surface, and, due to this review, 46% (56 out of
121) of all documented cases now come from Asia, thus
giving a more representative picture.
Naturally, reporting bias is likely to be considerable
for rare natural history events like these, and Brooks
(2012) therefore emphasized “the importance of report-
ing interesting natural history notes and keeping good
field records.” An example of positive reporting bias is
likely to be Taiwan. At 35,883km2, Taiwan has only 0.08
and 0.02% of the terrestrial surface of Asia and the Earth,
respectively. However, the 16 cases reported from Taiwan
(Table1) represent 29% of all Asian and 13% of all global
cases. One reason may be that large spiders are certainly
common in Taiwan Island, and especially in somewhat
disturbed or semi-open habitats with many small gaps and
openings suitable for building webs, such as the coastal
forests at Bitou Cape (cf. Table 1) where a large spider
web can be seen approximately every 10m. Accordingly,
Brooks etal. (2008) and Brooks (2012) hypothesized that
disturbed habitats, e.g. forests disturbed by severe storms,
may see an increase in the number of large spiders in the
lower strata, as possible attachment sites for webs were
destroyed in the upper strata, and Taiwan is regularly sub-
jected to devastating typhoons. Furthermore, Taiwan has
a very active bird-watching community and widespread
internet use, evidenced by the fact that 10 of the 16 Tai-
wanese cases were reported on the internet (Table1). e
internet and citizen-science can thus play an increasing
role in gathering and disseminating natural history infor-
mation (e.g. Sullivan etal. 2014; Lin etal. 2014).
Certainly, a bird being caught in a spider web remains a
rather rare event. I never encountered such a case in several
years of birdwatching in tropical and subtropical regions,
and 58 out of 68 people (85%) who replied to my request
for information also never encountered such a case. e
remaining people had only encountered one case in their
entire life except for Amar-Singh H., S. Pande, P. Round, G.
Welch, and C.-t. Yao who each had encountered two (this
does not include the multiple cases reported in the publica-
tions of Boedijn 1933; Manchi and Sankaran 2009; Kasambe
etal. 2010). For any small bird, it is nevertheless a consider-
able risk because it carries the highest fitness cost, i.e. death.
Combined with the facts that some spider species attempt
to make their webs more visible to birds (Bruce etal. 2005;
Walter and Elgar 2011), presumably to avoid collisions and
the consequent damage to their webs, and that small bats
are also at risk of spider predation (Nyffeler and Knörns-
child 2013), the risks of collision, entanglement or death
are probably high enough to facilitate the evolution of some
avoidance behaviour in small birds. Even for larger bird spe-
cies, there may be fitness costs; a 142g Hooded Butcherbird
(Cracticus cassicus) had to spend several minutes to preen
itself after a collision with a spider web (Brooks 2012). To
even begin to evaluate the magnitude of this risk, continu-
ous video monitoring of spider webs would be required to
establish collision frequencies, or captive birds could be
used in experimental settings with spider webs.
Table 2 Mean body masses andmean wing chord lengths ofbirds caught inspider webs inAsia (Table1) andthe world
(Table1; Brooks 2012); naturally, cases ofunidentied bird species inTable1 were excluded
The analyses were also split into individuals (i.e. all cases) and species (i.e. one case for each bird species). Each entry for body mass and wing chord length gives the
mean±standard deviation and the range in brackets
Analysis (sample size) Spider species Mass (g) Wing (mm)
Asia
Individuals (n = 49) 3 15.9 ± 13.7 (7.1‒80.0) 68.9 ± 20.9 (38.0‒138.0)
Species (n = 33) 3 17.5 ± 16.2 (7.1‒80.0) 73.1 ± 23.6 (38.0‒138.0)
World
Individuals (n = 114) 12 12.3 ± 10.8 (2.0‒80.0) 63.3 ± 20.1 (37.0‒138.0)
Species (n = 84) 12 13.5 ± 11.8 (2.0‒80.0) 66.4 ± 21.8 (37.0‒138.0)
Fig. 1 Frequency diagram of body mass intervals (in steps of 10 g)
of 49 cases (black bars) from Asia (Table 1) and the remaining 65
cases (grey bars) from other continents (Brooks 2012), whereby each
case involves one individual bird getting caught in a spider web as
described in the text

Page 7 of 7
Walther Avian Res (2016) 7:16
Conclusions
is study adds to the previously presented evidence
(Brooks 2012) that small birds face a risk of injury or death
wherever large spiders build large spider webs. Although
we can assume that these events are relatively rare com-
pared to other risks of death (e.g. predation by hawks,
snakes, or humans), what remains unknown is the fre-
quency of these events, and thus the evolutionary pressure
for the evolution of countermeasures in birds. Future stud-
ies should also elucidate if spiders carry a cost (damaged
web) or a benefit (additional prey) from these events, and
if their web building strategies have accordingly become
adapted to account for these presumably rare events.
Acknowledgements
I acknowledge the great help I received from my sources and translators,
namely Amar‑Singh H.S.S., Stephen Awoyemi, Anthony Bain, Daniel Brooks,
Geoff Carey, Yun‑Peng Chiang, Yu‑Wen Emily Dai, Martin Hale, Yu‑Cheng Hsu,
Masayoshi Kamioki, Raju Kasambe, Manh Hung Le, Yong Ding Li, Wich’yanan
Limparungpatthanakij, Hui‑Shan Lin, Ruey‑Shing Lin, Miyuki Mashiko, Satish
Pande, Merrin Pearse, Sander Pieterse, Himanshu Rathore, Philip Round, Rich‑
ard Thomas, Bas van Balen, Geoff Welch, Martin Williams, Jian‑Long Wu, Tsai‑Yu
Wu, Cheng‑te Yao, and Barure Nirmala of the Bombay Natural History Society
library, all of whom I thank profusely. I also greatly thank Nancy Greig, Mark
Harvey, Peter Jäger, Matjaž Kuntner and Adalberto Santos for spider identifica‑
tions, and Peter Capainolo, Anita Gamauf, Paul Sweet, Till Töpfer, Tom Trom‑
bone, and Hein van Grouw for helping to obtain measurements from bird
specimens. I also thank two anonymous reviewers for insightful comments.
Competing interests
The author declares that he has no competing interests.
Funding
I acknowledge financial support from Taipei Medical University through a
SEED Grant.
Received: 21 June 2016 Accepted: 20 August 2016
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