I. Living of feather mites
II. Living of quill mites
III. Living of feather follicle mites
I. Living of feather mites
Feather mites permanently inhabit the plumage of birds, where also the entire development cycle of the mites is taking place. In individuals with low infestation, mites are mainly settling on large feathers, where they are most likely to be found on flight feathers of wing then on feathers of tale. Yet, there can be observed species specific differences concerning the location on the host bird. Therefore, one can find Megninia columbae quite often on feathers of tail in pigeons, whereas another kind of feather mites in pigeons, Falculifer rostratus, obviously prefers flight feathers of wing. On a severely infested Mulga Parrot, for example, we have been able to find Dubininia melopsittaci almost on the entire feather coat, including the small plumage of the pectoral region.
picture: Megninia columbae tail feather
picture: Infestation with feather mites Falculifer pigeon
Dubinin (1951) dealt with the rules of distribution of mites in the feather coat. Several factors are influencing the whereabouts of mites and one can assume that there is a typical localization for each genus of mite, sometimes even species specific differences within one genus.
In cormorants, for example, three species of mites can be found. Alloptes subcrassipes spreads along up to the 20th flight feather, having its maximum on the 10th, Megninia phalacrocoracis along the 4th up to the 8th (maximum on the 5th) and Michaelichus heteropus along the 1st up to the 7th (maximum on the 3rd and 4th). Concerning the location in common swifts and night heron, details can be found in the chapter Detection of feather mites.
picture: feather with Proctophyllodes glandarinus hawfinch
Reproduction of feather mites is a sexual process. Most mite genera are oviparous, meaning they are laying eggs after insemination. Others, for example Freyana anatina are viviparous, they give birth to larvae.
Often, eggs are placed underneath small feathers, such as the large or small covert feathers of wing or tail, mainly between the barbs of feather. Sporadically, eggs placed on the upper side of feathers can be detected. Various species of mites also place their eggs between the radii of flight feathers of wing and feathers of tail, and in some cases directly onto the shaft of the feather. Depending on the density of infestation, eggs are placed in rows, or 2 to 3 eggs are laid next to each other or next to abandoned egg shells. Eggs appear translucent and clear after having been laid. During their course of development, they turn turbid, structures are starting to form inside and a double layer membrane appears. In the later development cycle, eggs are showing evenly spread, bright structures.
picture: feather of melopsittacus with eggs from Sideroferus
picture: eggs from feather mite Scutomegninia feather from cormorant
picture: egg from Sideroferus lunula
Larvae are leaving the eggs on the egg pole showing towards the side of the feather. In the same way nymphs are leaving their “old coats”. Using their hind legs, larvae blast the egg shell and leave it backwards. After a short time of poising, hatched individuals are starting to move. The abandoned egg shell sometimes looks like a recently laid egg, possibly leading to the result of misinterpretation. When viewing through microscope it might be useful to change the direction of light several times in order to spot the point of emergence.
According to Perez (1997), one can draw conclusions concerning the species of mite when considering egg morphology, position of the egg and alignment towards the feather shaft.
Larvae and following 2 stages of nymphs, as well as adult mites commonly use the feather as habitat. A favoured place of several species of mites is the junction of barbs of the feather shaft. In this angle, mites are resting motionless. These places are also looked up by nymphs in order to perform moulting to the next stage of nymph or in order to become an adult mite. Yet, this is only the case when birds are not severely infested. Otherwise, there are not enough of these preferred places.
Other species of mites also use the open access to the feather shaft or rachis and persist in there. Mesalgoides ocinum, a mite species occurring in Eurasian Bullfinch, reaches the hollow shaft through physiologically open Umbilicus superior.
Eichler (1954) describes another spot on the feather preferred by mites: "When occupying with mallophaga (biting lice), I detected another sort of relation between biting lice and mites. Feathers of exotic birds are often littered with empty egg shells of biting lice. Quite often, mites have settled within them. In the first instance they are used as a sort of shelter, similar to a dog house. Yet, sometimes mites can also be found in pairs, leading to the conclusion that they might have used the empty shell as a place for reproduction."
The spreading of mites and infestation of other birds usually occurs during nestling period, since adult birds and nestlings then have close contact. According to our observation, the chicks of Budgerigar and Mulga Parrot are being infested between the 3rd and 4th week. At this point of time, the vanes of feather are already developed more than one centimetre in size. In Agapornis taranta, the Mountain Parrot, vanes of feather evolve later, and therefore, the time of infestation is differed as well. This shows that the time of infestation directly correlates with nestling period and the development of the vanes of feather. Concerning Dubininia melopsittaci, we could find larvae, nymphs, as well as adult mites firstly infesting chicks of Budgerigar and Mulga Parrot.
Other possible ways of infestation are close contact, such as when looking up the same sleeping caves, during mating, as well as the common use of sand bathing locations. Concerning mites typical in Cuckoo, mating is the only relevant way of spreading. This rule can also be applied for feather lice in Cuckoo.
Eichler (1954) observed that female mites attached to feather lice themselves or attached their eggs to feather lice, using them as a transport medium.
Considering our results, development cycle of Dubininia melopsittaci lasts more than 4 weeks.
After the death of the host bird, feather mites show different patterns of behaviour. Some species leave moulting feathers, plucked feathers or death birds immediately, others stay on the feathers. So for example, we were able to detect living mites on a wing of a hooded crow, which had been stored in a garden hut for 2 months.
Feather mites are very resistant against low temperatures for several weeks. Frequently, we store samples of feathers in a refrigerator. The viability of mites is not negatively impacted through this process. Mites even survive temperatures below zero degree Celsius for some days. The following mite species survived on a starling which for a period of 3 days had been subjected to permanent frost (about 5 degrees Celsius below zero): Analges sturninus, Stornotrogus truncatus and Trouessartia rosterii. On a Blackbird which had been found dead at a temperature of 11 degrees Celsius below zero and stored outside at a temperature of 10 degrees Celsius below zero, living mites had been found after 14 days (Proctophyllodes musicus). On day 17, now thaw period, mites had left the marked feather areas. Yet, warmth and aridity negatively affect the survivability of mites.
Dubininia melopsittaci, a mite species parasiting on psittacine birds, in our opinion belongs to quite agile representatives of mites. In the middle of motion, these specimen suddenly rest when approaching a "cliff", such as straddled barbs of feathers. Then, they continue walking along the feather barb, constantly groping their way, looking for solid ground. Once having found solid ground, they cross the "dangerous place" immediately. This motion activity can be observed in all stages of development cycle. Yet, in literature, only larvae are considered to have higher motility.
Concerning nutrition, little firmed knowledge is existent. Normally it is stated that mites feed from the secretion of preen gland, skin flakes or feather particles.
Haller (1878) describes: "The content of the stomach shines through the body covering and seems to consist of epithelial flakes, feather residue, parts of glandular secretion and similar things. In rare cases, the middle part of the digestion tract is filled with red masses; when observing closer, these masses prove to be coagulated blood, which the mites have taken up during feeding on injured locations".
Other authors also include bacteria in the spectrum of nutrients, which are supposed to decay the secretion of the preen gland.
We do not like the thesis that the secretion of preen gland is the only feed of feather mites because many species of birds have not a preen gland.
According to Lapage (1956) mites of the genus Megninia feed from horn substance and excretions of skin. Also Hiepe (1962) found destruction of feathers caused by Megninia in a stock of ducks. One can assume that radii or at least parts of them serve the mites as nutrients.
We have been able to watch Dubininia melopsittaci feeding on tissue residue and interstitial fluid for a longer period of time on a feather which had been plucked out from a shortly before in an accident killed bird.
Feather mites are said to be highly host specific. Virtually, each bird species has got its own mite species. The mite Sideroferus lunula, for example, has (in our experience) only been found on Budgerigars, also in literature no other host has been described. Dubininia melopsittaci, the second mite species occurring on Budgerigars has been found on 12 different parrot species, on birds originating from all prevalence regions, such as America, Africa, Australia and New Zealand (Look up on Gallery). Yet, one has to take into consideration that all infested parrots had been kept under human care for a long period of time and therefore spreading among these different host birds might have been promoted. 36 out of 51 detected mite species have only been found on one single host bird, 15 had at least 2 different host species, which are in most cases related, such as black bird and field fare, for example.
The fact that closely related birds are infested by the same mite species led to phylogenetic investigations considering parasites on birds by an international team of scientists at the College of Vechta (Prof. Dr. Ehrnsberger, Dr. Dabert from Poland, Dr. Mironov from Russia) since 1995.
Haller (1878) already realized the relevance of feather mites on phylogenetics. In his paper on Freyana and Picobia he concludes: "Anyhow, it seems and I am delighted to conclude with this hope for future, that feather mites, which had been ignored for a long period of time, might be determined to contribute to clear up theories about the origins of species."
The number of parasites harboured by a bird depends on several factors. We have observed that young birds after preliminary contacts are showing a high extend of infestation in the following time. We have not been able to confirm the known fact that parasites mainly spread on hosts in critical condition, concerning the infestation with Dubininia melopsittaci.
During moulting time of starlings (in July), birds are six times less severely infested by mites than in May. According to Sechnow (1949), the infestation of Jackdaws reaches its top level during summer. A decrease occurs in winter, obviously due to low temperatures. There can also be noted a regression of infestation during moulting time (September through October).
Mites and eggs would be repelled through intense bathing. Jackdaws frequently bath during spring time and early summer.
The feather mite Freyana anatina, widely spread among ducks, leaves the vane of feather short before the loss of the old flight feather. It crawls down along the feather shafts and intrudes into feather follicles, than circularly establishing around the calamus of the juvenile, still growing feather. The place is only being left as soon as the feather has fully developed. This foresight is necessary since ducks moult all flight feathers at once, which would lead to a total loss of mite existence.
According to Jovani and Serrano (2001), having examined 13 mite species, mites leave these feathers, which are eliminated in the next step during moulting. Yet, we have found a vast number of mites on moulted feathers, so we cannot confirm this statement concerning other bird species.
II. Living of quill mites
Quill mites, occasionally termed feather shaft mites are little known parasites of birds. In literature, only little firmed knowledge about biology, host speciftiy, adverse effects and development cycle can be found. Most available data bases on presumption. Further, one should be careful to transfer unverified data from one species of quill mites to others, since there are definitely differences within Syringophilidae. Especially in older literature, confusion concerning quill mite species may occur since before the revision of Syringophilidae by Kethley (1970), many feather shaft mite species had been by mistake described as Syringoohilus-species. Another source of error may be the description of living of feather mites in the feather shaft, such as Ayringobia, Dermoglyphus or Cystoidosoma. In veterinary-parasitological or ornithological standard literature one can only find evidence that quill mites mainly live in the calamus of flight feathers of wing and feathers of tail in fowl, turkey, pigeon and wild birds. The most frequently named species is Syringophilus bipectinatus. All, up to this point of time known species of feather shaft mites inhabit the calamus with all their development stages. Only some specimens of the genus Picobia have been found in subcutaneous tissue of the wing. Quill mites seem to have a high host specifity (Kethley, 1970).
Infestation: The number of feathers attacked by mites strongly varied in our investigations. Quite often, only a singe feather had been affected, sometimes one flight feather of wing on each wing. On the other hand, sometimes a large number of feathers; flight feathers of wing and tail as well as covert feathers of wing, had been infested. In one adult sparrow (Passer domesticus) we detected seven infested flight feathers of hand on one wing (2nd, 3rd, 5th, 6th, 7th, 9th and 10th flight feather) and 4 infested flight feathers of arm (2nd,3rd,6th,7th). Furthermore, 5 feathers of the tail had been infested by quill mites. The degree of infestation on one feather strongly varied according to the time of infestation. When counting severely affected feathers, we came to the following conclusion concerning one flight feather of each species:
- Chaffinch (Fringilla coelebs): 30 living individuals on Syringophilopsis fringillae, 4 of them male, 19 female, 6 nymph stages, 1 larva.
- Redwing (Turdus iliacus): 45 living individuals of Syringophilopsis sp.; 9 male, 10 female, 19 nymph stages, 3 larvae and 3 eggs.
On two sparsely infested flight feathers of a Chaffinch, once we could find 2 and once only one female feather quill mites. According to Kethley (1970), shaft mites prefer different types of feathers, depending on several characteristics of the feather, such as volume of the shaft, thickness of the shaft wall or frequency of moulting. Other criteria influencing the choice of feathers are in his opinion: number of mite generations in the feather shaft, motility of the mite species and the ability of drilling holes in order to invade the feather shaft. These factors also enable the occurrence of 2 or 3 different mite species on the same host bird, then preferring different feather types.
Spreading of feather shaft mites is most likely to occur through direct contact between host birds, for example during nestling period or during mating (Kethley, 1970).
The process of invasion of the calamus or the feather shaft is a different one in different quill mite species.
According to Dabert and Mironov (1999), mites reach the inside of the shaft either through the Umbilicus superior or through self made holes. Some mite species might be able to reach the inside of the feather via the papilla of the feather, since there could not be found any access ways in infested feathers. Other mites reach the calamus via drilled holes. Obviously, these holes also serve as exit ways. We have been able to observe feather shafts showing holes which had been begun to drill from the outside. Normally, the hole for a certain mite species can be found on the same spot, mostly at the beginning of the vane of feather, on the dorsolateral side of the shaft; yet, there can be irregularities. In the case of a crossbill (Loxia curvirostra), we found drilled holes both on the outer side of the vane and on the inner side of the vane along the calamus. In most cases, there is only one hole to be found per shaft, sometimes though, more than one. In a Song thrush (Turdus philomelos),
for example, we found 3 holes in a shaft, 2 of them next to each other. In a Robin (Erithacus rubecula), holes have been detected on the inner side of the vane, in a lower position on the shaft than in cases of other mite species, at the transition of skin covering part of the shaft to the free part.
picture: quill mite from the european goldfinch drilling a hole
The holes differ in diameter as well, depending on the mite species. The size of the hole of shaft mite Torotrogla sp. (occurring in Robins, Erithacus rubecula) has been 118µm, whereas the diameter of holes caused by another Torotrogla species occurring on Song thrushes (Turdus philomelos) measured about 176µm.
Nevertheless, exact determination of these two feather shaft mites has to follow. When measuring the shaft mites and their development stages in Song thrushes (Turdus philomelos), we could determine a width of in average 252µm in adults, 224µm in nymphs and 166µm in larvae. Eggs of these feather shaft mites have a round shape and double the size of a drilled hole, showing that the larvae only can pass the holes or older stages have a soft shell and therefore they are able to pass as well.
In addition, the holes can also serve other mite species as entrance possibilities, normally living on the feather surface. For example, we could find Proctophyllodes rubeculinus on Robin (Erithacus rubecula) together with quill mites in the calamus.
Concerning the species of Bullfinches (Pyrrhula), the Umbilicus superior on most of the flight feathers of wing and feathers of tail is enlarged, even if these birds are not infested by mites. This aperture is used by feather mites (Mesalgoides oscinum) to enter the feather shaft. Feather shafts are serving as whereabouts and are most likely to be used during moulting cycle, since spaces in the shaft are usually filled by residues of moulting. Therefore, one can assume an infestation by feather shaft mites when only skimming over.
Also Dabert and Ehrnsberger (1992) point out the meaning of Umbilicus superior for other feather mite species. They are describing the life cycle of Cystoidosoma psittacivora, appearing on Black headed caiques (Pionites melanocephalus) as follows:
"The life cycle of Ascouracaridae has been acquired through the example of Cystoidosoma psittacivora sp. n. in the plumage of Pionites melanocephalus (Psittacidea). Larvae of Cystoidosoma enter, like most mites infesting feather shafts, through Umbilicus superior. This is a cleft like opening of the feather shaft which can be found near the vane of feathers. Larvae moult in the inner side of the calamus. Just like in all other known feather mite species, all development stages are appearing: larvae, proto- and tritonymphs, males and females. In the beginning, mites only feed from the "Soul of the feather" in the calamus, which is eaten up completely. Also in the shaft, mites moult to become adult individuals. Adult mites are relatively large (more than 1 mm). In the shaft, only up to 5 adult mites can find space. Since in the shaft there are also moulting residues, faeces, as well as other mite species to be found, (Paralgopsis sp., Pyroglyphidae),
adult mites start to gnaw a walkway into the sponge like substance of the shaft. Diameter of this path is only slightly larger than the female mite’s idiosoma. In 2 or 3 spots one can find a dilatation along the path, probably in order to serve as a possibility to let one pass another. There is every indication that this is the reason, since up to 3 mites had been found in one corridor. The path may reach up to the tip of the feather, yet, it ends at the place where the inner diameter of the feather is as large as the width of the idiosoma of the mite. In some cases, the corridor bends half way and continues proximal. Mating probably takes place in the feather shaft. Female mites lay up to 50 to 70 eggs into the shaft. The chorion is a thin and membranous layer through which the almost developed larva can be seen. Female mites prepare an exit for the larvae in the region of the corridor. Mostly near the inner vane of the feather, about 3 cm from the feather base.
Here, they gnaw an excavation to the side wall and larvae themselves own strong and cutting chelicerae helping them to gnaw a cleft like opening into the middle of the excavation. There has been no indication whether all larvae use this hole to exit the feather of if some larvae leave the feather via Umbilicus superior. Possibly, the life cycle of Ascouracaridae more or less differs form the life cycle of Cystoidosoma psittacivora, which had been described in this place. Larvae of Ascouracarus kosarovi, for example in most cases actively enter through the wall of the feather shaft (Mironov, personal notification).
Investigations of Dabert and Ehrnsberger (1993 and 1995) show that it is not always feather shaft mites being responsible for holes located in the shaft. The way of life of Dermoglyphus giganteus, a feather mite species living in the calamus of Columbigallina passerina, has been reconstructed. Quotation: "Feather mites have been found in the calamus of Columbigallina passerina. In the material, only females and larvae have been found; no egg shells, moulting residues, nymphs or males have been evident. Normally, these can be found inside the calamus. Inside the calamus, only a huge female and sometimes a larva have been detected. Females have always been located at the base of the feather, with their front facing towards the papilla of the feather. Between the papilla of the feather and the female mite, one can find homogeneous, slightly structured masses, which in our opinion are encrusted lymphoid liquid. The lymph might have been exsudated from the papilla into the lumen of the shaft and serve the mite as nourishment. Injuries of the wall of the calamus have not been detected. Within the feather shaft, a small, round hole (200µm) can be found, located approximately 5 cm away from the feather base, in the groove on the ventral side of the feather. From this hole, a corridor expands up to the calamus. In our opinion, this hole represents the entering opportunity, since from this location, a gnawing path continuously widens until reaching the calamus. A large amount of droppings can be found in this gnawing channel and in the calamus. Yet, due to limited existing material, it is hardly possible to draw final conclusions concerning the spreading of the mites. The hole is larger than the diameter of the larva, meaning that the larvae cannot be seen as the spreading stage. Furthermore, larvae have a very thin skin and do not show special morphological adjustments. Probably, nymphs or young (and therefore small) females leave the feather via the hole in the shaft. Yet, up to this point of time, it is not possible to say why we have only found larvae and huge female mites inside the feathers."
Little knowledge is available concerning the feeding habits of feather shaft mites. Trouessart (1885) stated that as soon as mites of the Syringobia genus (Fam. Cheyletidae) living inside the feather shafts get into contact with mites of Syringophilus genus, Syringobia are completely extinguished. Dubinin (1951) has proven this statement by the example of parasites on Redshanks (Tringa tetanus). As soon as a bird gets infested by Syringophilus bipectinatus, these mites kill already present Syringobia and later settle inside the shafts of all feathers, feeding from epidermal dandruff of the feather follicle. As soon as Syringobia mites reach host birds that are already infested by Syringophilus, they are immediately eaten up by the latter. Also according to Gruner (1993), feather shaft mites feed from other inhabitants of the feather or from lymph of the host bird. Fritsch (1958) as well, assumes that quill mites open the papilla with their mouth part and suck up the exsudating lymphoid liquid. According to Kethley (1970), quill mites own long, needle like chelicerae and feed from the tissue of the wing once they have drilled through the calamus. Clark (1963) states, that the structure of mouth parts is made for stinging into the soft, strongly vascularized tissue of the wing.
Yet, there is further scientific research necessary in order to receive reliable knowledge concerning nutrition, infestation, development cycle, life span and further more of feather shaft mites.
Clark, G.M. (1964): The acarine genus Syringophilus in North American birds. Acarologia 6: 77-92.
Dabert, J. und R. Ehrnsberger (1992): Neue Arten bei der Federmilbenfamilie Ascouracaridae Gaud und Atyeo, 1976. Osnabruecker naturwiss. Mitt. 18: 109-150.
Dabert, J. und R. Ehrnsberger (1993): Dermoglyphus giganteus sp. nov., eine neue Art der Federmilben aus der Familie Dermaglyphidae (Astigmata, Analgoidea) vom Sperlingstäubchen Columbigallina passerina (Aves, Columbiformes). Osnabruecker naturwiss. Mitt. 19: 71-77.
Dabert, J. und R. Ehrnsberger (1995): Vassilievascus gen. nov., a new genus of the family Ascouracaridae Gaud und Atyeo, 1976 (Astigmata;Pterolichoidea). Osnabruecker naturwiss. Mitt. 20/21: 95-100.
Dabert, J. und S.V. Mironov (1999): Origin and evolution of feather mites (Astigmata). Experimental and Applied Acarology 23: 437-454.
Dubinin, W.B. (1951): Die Federmilben (Analgesoidea). Teil I. Einführung in ihre Untersuchung. „Fauna SSSR“, Bd.&, Lief. 5. Verl. Akad.Nauk. SSSR.
Eichler, Wd. (1954): Milben on Mallophagen. Rivista di Parassitologia Vol.XV-N.4-Ottobre.
Fritsch, W. (1958): Die Milbengattung Syringophilus Heller 1880 (Subordo Trombidiformes, Fam. Myobiidae Megnin 1877). Zool. Jahrbücher 86, 227-244.
Gruner, H.-E. (Hrsg.) (1993): Lehrbuch der Speziellen Zoologie. Bd.I Wirbellose Tiere, 4.Teil Arthropoda (ohne Insecta), Gustav Fischer Jena – Stuttgart.
Haller, G. (1878): Freyana und Picobia. Zwei neue Milbengattungen. Zeit. Wiss. Zool. 30: 81-98. Verlag Wilhelm Engelmann, Leipzig.
Hiepe, Th., Ebner, D. und Buchwalder, R. (1962): Vorkommen, Schadwirkung und Bekämpfung des Megninia- Befalles bei Enten. Monatshefte für Veterinärmedizin 17: 605-610.
Jovani, R. and Serrano (2001): Feather mites (Astigmata) avoid moulting wing feathers of passerine birds. Animal Behaviour 62: 723-727.
Kethley, J.B. (1970): A revision of the family Syringophilidae (Prostigmata: Acarina). Contributions of the Am. Entomol. Inst. 5: 3-75.
Perez, T.M. (1997): Eggs of feather mite congeners (Acarina: Pterolichidae, Xolalgidae) from different species of new world parrots (Aves: Psittaciformes). Intern. Journal of Acarology, 23: 103-106.
Sechnow, M.J. (1949): Die Dynamik der Parasitenfauna der Dohle. Utschjen. Dap. Wologochkowo Pädag. Inst. 5 (Biol.): 29-116.
Trouessart, E. (1885): Les Sarcoptides plumicoles. J.Microgr. 9: 63-70, 109-117.