Editing Common blackbird (section)

===Natural threats===
[[File:Blackbird and Kestrel.jpg|upright|thumb|A male blackbird attempting to distract a male [[Common kestrel|kestrel]] close to its nest]]
Near human habitation the main predator of the common blackbird is the domestic cat, with newly fledged young especially vulnerable. Foxes and predatory birds, such as the [[Eurasian sparrowhawk|sparrowhawk]] and other [[accipiter]]s, also take this species when the opportunity arises.<ref name=RSPB/><ref name=Lambeth>{{cite web |title= Blackbird Action Plan |url= http://www.lambeth.gov.uk/NR/rdonlyres/A862EBE6-4CD7-4317-9B64-D0FB565AAF1C/0/BAPSummaryBlackbird.pdf |publisher= Lambeth Council's Parks and Greenspaces Business Unit |access-date= 11 December 2007 |url-status= dead |archive-url= https://web.archive.org/web/20071005010251/http://www.lambeth.gov.uk/NR/rdonlyres/A862EBE6-4CD7-4317-9B64-D0FB565AAF1C/0/BAPSummaryBlackbird.pdf |archive-date= 5 October 2007 }}</ref> However, there is little direct evidence to show that either predation of the adult blackbirds or loss of the eggs and chicks to [[Corvidae|corvids]], such as the [[European magpie]] or [[Eurasian jay]], decrease population numbers.<ref name=NatEngland>{{cite web |title = Blackbird – ''Turdus merula'' |url = http://www.joyofplants.com/wildlife/search.php?o=30 |publisher = The Royal Horticultural Society/The Wildlife Trusts |access-date = 9 April 2012 |url-status = dead |archive-url = https://web.archive.org/web/20131029203048/http://www.joyofplants.com/wildlife/search.php?o=30 |archive-date = 29 October 2013 }}</ref>

This species is occasionally a host of [[brood parasite|parasitic]] [[cuckoo]]s, such as the [[common cuckoo]] (''Cuculus canorus''), but this is minimal because the common blackbird recognizes the adult of the parasitic species and its [[mimicry|non-mimetic]] eggs.<ref name = daviesnb>{{cite journal | last1=Davies | first1=N. B. | last2=Brooke | first2= M. de L. | year=1989 | title= An experimental study of co-evolution between the Cuckoo, ''Cuculus canorus'', and its hosts. I. Host egg discrimination | journal= Journal of Animal Ecology | volume=58 | issue=1 | pages=207–224 | jstor=4995 | doi=10.2307/4995| bibcode=1989JAnEc..58..207D }}</ref> In the UK, only three nests of 59,770 examined (0.005%) contained cuckoo eggs.<ref name= glue>{{cite journal |last= Glue |first=David |author2=Morgan, Robert |year=1972 |title= Cuckoo hosts in British habitats | journal= Bird Study | volume= 19| pages=187–192 |doi=10.1080/00063657209476342|issue=4|bibcode=1972BirdS..19..187G }}</ref> The introduced ''merula'' blackbird in New Zealand, where the cuckoo does not occur, has, over the past 130 years, lost the ability to recognize the adult common cuckoo but still rejects non-mimetic eggs.<ref name=JAB>{{cite journal|last=Hale|first=Katrina|author2=Briskie, James V.|date=March 2007|title=Response of introduced European birds in New Zealand to experimental brood parasitism|journal=Journal of Avian Biology|volume=38|issue=2|pages=198–204|issn=0908-8857|doi=10.1111/j.2007.0908-8857.03734.x|url=http://www.biology.ualberta.ca/courses.hp/biol506.hp/pdfs/Hale07_JAvBi_BroodParasitism.pdf|access-date=2012-01-16|archive-url=https://web.archive.org/web/20120113014727/http://www.biology.ualberta.ca/courses.hp/biol506.hp/pdfs/Hale07_JAvBi_BroodParasitism.pdf|archive-date=2012-01-13|url-status=dead}}</ref>

As with other passerine birds, parasites are common. [[Intestinal parasite]]s were found in 88% of common blackbirds, most frequently ''[[Isospora]]'' and ''[[Capillaria (nematode)|Capillaria]]'' species.<ref>{{cite book|last=Misof|first=Katharina|url=http://hss.ulb.uni-bonn.de:90/2005/0661/0661.pdf|title=Eurasian Blackbirds (''Turdus merula'') and their gastrointestinal parasites: A role for parasites in life-history decisions?|publisher=Doctoral dissertation, Bonn|year=2005|url-status=dead|archive-url=https://web.archive.org/web/20110719101955/http://hss.ulb.uni-bonn.de:90/2005/0661/0661.pdf|archive-date=2011-07-19}}</ref> and more than 80% had haematozoan parasites (''[[Leucocytozoon]]'', ''[[Plasmodium]]'', ''[[Haemoproteus]]'' and ''[[Trypanosoma]]'' species).<ref>{{cite journal |author1=Hatchwell, B. J. |author2=Wood |author3=Anwar, M. J. M. |author4=Perrins C. M. |url=http://www.nrcresearchpress.com/doi/abs/10.1139/z99-228?journalCode=cjz |title=The prevalence and ecology of the haematozoan parasites of European blackbirds, ''Turdus merula'' |journal=Canadian Journal of Zoology |volume=78 |issue=4 |pages=684–687 |year=2000 |doi=10.1139/cjz-78-4-684|url-access=subscription }}</ref>

Common blackbirds spend much of their time looking for food on the ground where they can become infested with ticks, which are external parasites that most commonly attach to the head of a blackbird.<ref name= Gregoire/> In France, 74% of rural blackbirds were found to be infested with ''[[Ixodes]]'' ticks, whereas, only 2% of blackbirds living in urban habitats were infested.<ref name= Gregoire/> This is partly because it is more difficult for ticks to find another host on lawns and gardens in urban areas than in uncultivated rural areas, and partly because ticks are likely to be commoner in rural areas, where a variety of tick hosts, such as foxes, deer and boar, are more numerous.<ref name= Gregoire/> Although ixodid ticks can transmit [[pathogen]]ic viruses and bacteria, and are known to transmit ''[[Borrelia]]'' bacteria to birds,<ref name= Kipp>{{cite journal|last= Kipp|first= Susanne |author2=Goedecke, Andreas|author3=Dorn, Wolfram|author4=Wilske, Bettina|author5=Fingerle, Volke |date=May 2006|title=Role of birds in Thuringia, Germany, in the natural cycle of ''Borrelia burgdorferi'' sensu lato, the Lyme disease spirochaete |journal= [[International Journal of Medical Microbiology]]|pmid= 16530003|volume= 296|pages= 125–128 |doi=10.1016/j.ijmm.2006.01.001 }}</ref> there is no evidence that this affects the fitness of blackbirds except when they are exhausted and run down after migration.<ref name=Gregoire>{{cite journal |last=Gregoire |first=Arnaud |author2=Faivre, Bruno |author3=Heeb, Philipp |author4=Cezilly, Frank |year=2002 |title=A comparison of infestation patterns by ''Ixodes ''ticks in urban and rural populations of the Common Blackbird ''Turdus merula'' |url=http://www.cefe.cnrs.fr/esp/publis/AG/AGGregoire%20et%20al%202002%20Ibis.pdf |journal=Ibis |volume=144 |issue=4 |pages=640–645 |doi=10.1046/j.1474-919X.2002.00102.x |url-status=dead |archive-url=https://web.archive.org/web/20081217155251/http://www.cefe.cnrs.fr/esp/publis/AG/AGGregoire%20et%20al%202002%20Ibis.pdf |archive-date=2008-12-17 }}</ref>

The common blackbird is one of a number of species which has [[unihemispheric slow-wave sleep]]. One hemisphere of the brain is effectively asleep, while a low-voltage [[Electroencephalography|EEG]], characteristic of wakefulness, is present in the other. The benefit of this is that the bird can rest in areas of high predation or during long migratory flights, but still retain a degree of alertness.<ref name="Perspectives">{{cite journal |last1=Rattenbourg |first1=Neils C. |last2=Amlaner |first2=C. J. |last3=Lima |first3=S.L. |title=Behavioral, neurophysiological and evolutionary perspectives on unihemispheric sleep |journal=Neuroscience and Biobehavioral Reviews |volume=24 |pages=817–842 |year=2000 |pmid=11118608 |doi=10.1016/S0149-7634(00)00039-7 |issue=8|s2cid=7592942 }}</ref>