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Generalist Aphid Predator (Passeriformes: Paridae)Parus majorGreat titOn this page: Identification & Distribution Biological Control of Aphids Predation of aphid galls Factors affecting aphid predation Vertebrate predation can be a headacheIdentification & DistributionMales of Parus major (see first picture below) have a bluish-black crown, a black neck, throat, bib and head and white cheeks and ear coverts. The breast is bright lemon yellow and there is a broad black mid-line stripe running from the bib to the vent. Most of the nape and back are greenish, but there is a dull white patch on the neck. The wing coverts are green and the rest of the wings is bluish-grey with a white wing-bar. The tail is bluish grey with white outer tips. The female (see second picture below) has slightly duller colours and the line running down the belly is narrower and sometimes broken. Immatures resemble females, but with a dull olive brown nape and neck and a grey tail. The various Parus major subspecies, of which there are fifteen, differ somewhat in colour.
First image male: Copyright Jean-Jacques Boujot under a Creative Commons Attribution-Share Alike 3.0 License The great tit is found in a range of habitats from dense to open deciduous and conferous woodland, riverine forest, scrubland and gardens. Parus major is found across most of Europe, North Africa, the Middle East and parts of central Asia. Biological Control of AphidsParus major are not major predators of free-living aphids, but are known to frequently predate gall-living aphids. Predation of aphid gallsPerrins (1979) noted that Parus major "show considerable ingenuity when it comes to reaching food in difficult sites". This is demonstrated by various observations of great tits predating aphids in galls. In his blog on Kensington Gardens and Hyde Park birds, Ralph Hancock describes how he spotted a great tit carrying a leaf on a long stem with something attached to the stem. The attachment was subsequently identified as a gall of the spiral leaf gall aphid (Pemphigus spyrothecae, see below).
Image reproduced by permission, copyright Ralph Hancock all rights reserved The gall is packed full with aphids. The image below shows the aphids inside a gall of Pemphigus bursarius, a closely related species.
After opening the gall with their stout beak (which is especially-adapted to seed eating), the great tits either consume the aphids themselves or feed them to their nestlings. Burstein & Wool (1992) were the first to report that Parus major exploit aphid galls as a source of food. The great tits were initially feeding on galls of the aphid Paracletus cimiciformis (see first picture below). Ninety percent (or 75/83) of the galls bore clear puncture marks, and some were emptied of aphids. In others, the predator had not been completely successful and live aphids remained inside. Only eight fallen galls were intact. The behaviour of Parus major was observed directly. A pair was seen flying from tree to tree in the neighbourhood. The bird moved on the branches, located a leaflet with an aphid gall, held it in its beak and removed it from the leaf. It moved to a larger branch, held the leaf down with its foot, and with quick and well-directed strokes of the beak, opened the gall and ate its contents. The handling of one gall took less than 30 seconds. Both partners pursued this activity for 12 minutes and handled six galls during this time period. The authors collected a total of 182 leaflets carrying Paracletus galls under the tree. Of these, 143 (79%) had been preyed upon by the tits.
Both images reproduced by permission, Copyright Nicolás Pérez, all rights reserved In late October, the birds started to attack galls of the more common gall-forming aphid Forda formicaria (see second picture above), which were absent in the first two samples. This species seems to be used less by the birds (just 139 of 244 galls collected (57%) were consumed). The birds' switching to Forda formicaria at the end of the season is very interesting given that Forda formicaria and Paracletus galls may occur on the same leaves. Perhaps when Paracletus galls became scarce, the birds searched for alternatives. In mid-October the Forda formicaria galls were beginning to open to release their aphids, which may have enabled the inquisitive tits to learn to associate the conspicuous Forda formicaria galls of this species with the presence of food. A Forda formicaria gall may contain 100-150 aphids; quite a rich source of insects for the birds. Factors affecting aphid predation by great titsCowie & Hinsley (1988) identified the prey brought by great tits (Parus major) for their nestlings by fitting cameras in the nestboxes. They showed there was no difference in the type of prey brought by males and females, but there were significant differences between great tits and blue tits (Cyanistes caeruleus). Great tits brought more spiders and flies, whereas blue tits brought more aphids. The diet of nestling great tits varied with age: young nestlings (3-9 days) being fed greater than expected numbers of spiders, earwigs and flies. Great tits brought more spiders than expected from 08.00 to 13.00 h, and more flies from 05.00 to 08.00 h. Many aphids are attended by ants, which are thought to provide a measure of protection against predators - especially small invertebrates. Haemig (1996) set up a field experiment in which great tits (Parus major) foraged on a pair of artificial trees that were supplied with equal amounts of ant food and bird food. Wood ants (Formica aquilonia) were excluded from one tree, but foraged on the other. Great tits visited the tree without ants more frequently, and for longer periods of time, than the tree with ants. The time of foraging visits by tits in the tree with ants decreased as ant activity there increased. These results were the first to show that interference competition from ants can influence a bird's choice of microhabitat in which to forage, as well as alter the time it spends foraging there.
The mechanism of interference was two-fold. First, wood ant bites are painful. On several occasions the author saw birds jump when an ant came into contact with one of their feet. Wood ants also spray formic acid, which can be both painful and momentarily debilitating. Malcolm (1986) used great tits in his experiments on aposematism with Aphis nerii - which birds find distasteful. The experiments were designed to test the suggestion that aposematism could arise by kin selection, since aposematic animals often occur in aggregations of relatives. Initially great tits killed a high proportion (54%) of Aphis nerii but, with experience, the predator killed and ate fewer of these aphids. Given that kin selection should be most efficient among very closely related individuals, the decreasing aphid mortality coupled with obligate parthenogenesis indicated that evolution of aposematism in this aphid was consistent with kin selection. There are further references in the literature to great tits eating aphids, although sometimes with little hard evidence. For example Banbura & Banbura (2012) state that both the great tit and the blue tit are flexible in their prey choice and opportunistially exploit abundant prey such as aphids in central Poland. Cramp et al. (1988) related sudden upsurges in numbers of several tit species, including the great tit in 1957, to an unusually mild winter in 1956-57 which enabled aphids in pine woodland to breed prolifically throughout January and February. Vertebrate predation by Parus major can be a headacheDarren Naish provides a somewhat different perspective on great tit feeding ecology in his Scientific American Blog: Tetrapod Zoology under the title "Great tits: still murderous, rapacious, flesh-rending predators!". He notes that whilst Parus major mostly feeds on insects and seeds, using its bill to break into hazelnuts and acorns. the bird is also an accomplished raider of caches created by other passerines, in particular those of the smaller marsh tit (Poecile palustris) and coal tit (Periparus ater). Unlike those species, the great tit does not usually hoard food. It is also a facultative tool-user, reported on occasion to use conifer needles to winkle insect larvae out of bark (Gosler, 1993), and a part-time scavenger, its habit of picking at the bones of hoofed mammals being well known (e.g. Selva et al., 2005). Rather less well known is that Parus major sometimes uses its relatively large size and powerful bill to kill smaller passerines. Barnes (1975) described two or three cases where pied flycatchers (Ficedula hypoleuca) were found dead with smashed skulls in nest-boxes taken over by great tits. Caris (1958) reported a case in which a great tit was seen flying away with a dead goldcrest (Regulus regulus) that had been killed by a peck to the back of the head. Its eyes were pecked out and its skull mangled. Saunders (1899) wrote that "The Great Titmouse [Parus major] will attack small and weakly birds, splitting their skulls with its powerful beak in order to get at their brains; and it has even been known to serve a Bat in this manner". In recent years, the killing and eating of bats by Parus major became internationally known after Estok et al. (2010) reported how great tits were finding hibernating bats in cavities in caves, bashing the bat's heads in, and eating their brains.
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_1ew.jpg "Female great tit (Parus major)")
