Demographic routes to variability and regulation in bird populations

There is large interspecific variation in the magnitude of population fluctuations, even among closely related species. The factors generating this variation are not well understood, primarily because of the challenges of separating the relative impact of variation in population size from fluctuations in the environment. Here, we show using demographic data from 13 bird populations that magnitudes of fluctuations in population size are mainly driven by stochastic fluctuations in the environment. Regulation towards an equilibrium population size occurs through density-dependent mortality. At small population sizes, population dynamics are primarily driven by environment-driven variation in recruitment, whereas close to the carrying capacity K, variation in population growth is more strongly influenced by density-dependent mortality of both juveniles and adults. Our results provide evidence for the hypothesis proposed by Lack that population fluctuations in birds arise from temporal variation in the difference between density-independent recruitment and density-dependent mortality during the non-breeding season.Peer reviewe

Orthocladius (Orthocladius) dentifer

Orthocladius (Orthocladius) dentifer (Figs. 70–74) Material examined NORWAY: Hordaland, Vaksdal, Ekse, 1 ɗ reared from larva, 2 Ψ reared from larva, 9 xi 1978, T. Andersen; same locality, 1 ɗ reared from larvae, 4 mature ɗ pupae, 5 vii 1979, E. Willassen (ZMBN). USA: Georgia, Rabun Co. West Fork Chattooga River, 1 ɗ, 10 v 1980. P. L. Hudson (ZMBN). Description Male imago As mentioned by Soponis (1977), the North American material mostly agrees with the European except for the smaller size and the distinct scutal stripes. In addition, at least the specimen from Georgia has only about 3 sensilla chaetica at 0.13–0.18 of ta 1 of mid leg and a 26 m long virga, while the specimens from Ekse have 10–14 sensilla chaetica at 0.05–0.07 to 0.13–0.18 and the virga is only 0–15 µm long. In all other counts and measurements the differences are not significant. Female imago (n = 3 except when otherwise stated) Total length 3.64–3.97 mm. Wing length 2.36–2.69 mm. Total length/wing length 1.45–1.54. Wing length/length of profemur 3.21–3.36. Head. AR 0.67–0.75. 0.71 (4). Flagellomere lengths (in µm, n= 4–6): 83 –86, 84; 53 – 56, 55; 49 –56, 47; 49 –56, 50, 161–180, 168. Flagellomeres 3 and 4 fused in one specimen. Temporal setae 8 –13, 10 (5); consisting of 3 –5, 4 inner; 5 –7, 6 outer verticals; and 0–3, 1 postorbital. Clypeus with 16 –19, 17 (5) setae. Tentorium 150–169 µm long, 26–30 µm wide. Stipes 150–161 µm long, 41–53 µm wide. Palpomere lengths (in µm): 38; 53–64; 105–124; 83–116, 101 (5); 143–199, 165 (5). Thorax (n = 6). Antepronotum with 8 –13, 10 setae. Dorsocentrals 7 –13, 10; acrostichals 14–16 (3); prealars 3 –6, 4; no supraalar. Scutellum with 8 –12, 10 setae. Wing. VR 1.05–1.11. Costal extension 56–75 m long. Brachiolum with 1 (6) seta; R with 11 –20, 16 (6) setae; R 1 with 6 –12, 10 (6), R 4 + 5 with 12 –20, 16 (6); costal extension with 1 –2, 1 (6) non­marginal seta. Squama with 16 –27, 21 (6) setae. Legs. Spur of front tibia 49 µm long, spurs of middle tibia 30–38 and 26–30 µm long, of hind tibia 60–79 and 26 µm long. Width at apex of front tibia 45–49 µm, of middle tibia 45–51 µm, of hind tibia 49–56 µm. Pseudospurs present on ta 1 of mid leg and hind leg and ta 2 of mid leg, 23–34 µm long. Sensilla chaetica 17–23 at 0.06–0.08 to 0.20–0.30 on ta 1 of mid leg, 7–17 at 0.06–0.07 to 0.17–0.26 on ta 1 of hind leg. Lengths (in µm) and proportions of legs: Abdomen (n = 6). Number of setae on tergites I–VIII as: 61 –73, 67; 36 –45, 40; 26 –38, 33; 25 –34, 31; 28 –34, 31; 23 –33, 27; 17 –29, 22: 17 –25, 21; on sternites I–VIII: 0; 2 –5, 4; 7 –11, 9; 10 –19, 13; 18 –25, 20; 20 –28, 23; 28 –31, 23; 22 –30, 27. Genitalia (Figs. 70–74, n = 5–6). Tergite IX strongly divided with margins clearly delimited, with 20 –31, 24 setae. Gonocoxite with 23 –34, 28 setae. Cercus 120–180, 160 µm long. Seminal capsule pear­shaped; 60 –78, 69 µm long; anterior 34 –45, 41 µm darker sclerotised; 45 –54, 50 µm wide. Spermathecal ducts slightly meandering with separate openings. Notum 116–150, 142 µm long. Remarks It is not unlikely that the Nearctic specimens represent a different species as evidenced by the differences in sensilla chaetica on the legs and the length of the virga. However, more material from a wider range of localities is needed before any conclusion can be drawn.Published as part of Saether, Ole A., 2005, A new subgenus and new species of Orthocladius van der Wulp, with a phylogenetic evaluation of the validity of the subgenera of the genus (Diptera: Chironomidae), pp. 1-56 in Zootaxa 974 on pages 52-54, DOI: 10.5281/zenodo.17131

Chironomus (Chironomus) entis Shobanov

Chironomus (Chironomus) entis Shobanov (Figs 3 A–C, 6 A–E, 7, 9) Chironomus (Chironomus) entis Shobanov, 1989 a, 1989 b: 341. Chironomus plumosus f. semireductus auct. pro parte Chironomus muratensis Chang et al. 1993, 1994, not Ryser, Sholl et Wülker. Material examined. Lake Winnipeg light traps: Matheson Island Government Wharf, 5 males, 3 females, 5.vi. & 26.vii. 1969; 4 km off Grand Rapids, 22 males, 8.vi. 1969; Victoria Beach, 110 males, 9.vii. & 25.vii. 1969; Pine Dock, 9 males, 10.vii. 1969; 0.5 km off George Island, 131 males, 11.vii. & 12.vii. 1969; 3 km off Grand Rapids, 1755 males, 13.vii. & 4.ix. 1969; 10 km off (Sturgeonskin point) Long Point, 4471 males, 14.vii. 1969; 3 km off McCreary Island, 344 males, 15.vii. 1969; Gull Harbour, 28 males, 5 females, 16.vii. 1969; Gimli Government Wharf, 197 males, 24.vii. 1969; 3 km off George Island, 1578 males, 1 female, 27.vii. 1969; Grand Rapids Government Wharf, 728 males, 28.vii. & 5.ix. 1969; 5 km off Selkirk (Horse) Island, 487 males, 29.vii. 1969; McBeth Harbour, 202 males, 30.vii. & 7.ix. 1969; Pine Dock, 5 males, 31.vii. 1969; 15 km E off Long Point, 6 males, 6.ix. 1969; Beaver Point, 413 males, 18.vi. – 27.viii. 1971; 20 Mile Creek, 2 males, 5.viii. 1971; Old Fishing Dock, 839 males, 9.vi. – 5.viii. 1971; Calder's Dock, 373 males, 11.vi. – 8.ix. 1971; Hecla Island, 12 males, 27.vii. & 11.viii. 1971. Emergence traps: Beaver Creek, 6 males, 22.vii. – 11.viii. 1971. Rearing specimens: NNE of Reindeer Island, 4 males, 11.vi. 1969; NW Disbrowe Point, 1 male, 11.vii. 1969; Saskatchewan River Buoy, 1 male, 13.vii. 1969; East of Selkirk Island, 1 male, 29.vii. 1969; West of Selkirk Island, 3 males, 29.vii. 1969; East McCreary Island, 3 males, 31.vii. 1969; Anama Bay, 1 male, 31.vii. 1969; 13 km SE Bigstone Point, 1 male, 1 female, 3.ix. 1969. South Basin, 55 larvae, 9.vii. – 31.x. 1969; Narrows, 302 larvae, 1 pupa, 4.vi. – 31.x. 1969; North Basin, 356 larvae, 8 pupae, 4.vi. – 31.x. 1969. Normal unparasitized males from Lake Winnipeg have an AR of 4.80–6.61, 5.46 (115); 30 –55, 36 (10) sensilla chaetica on p 2; 20 –36, 24 (10) sensilla chaetica on p 3; and fall completely within the redescription of C. plumosus (L.) by Strenzke (1959: 19). The females have 130–220, 178 (10) sensilla chaetica on p 2; 140–252, 217 (10) sensilla chaetica on p 3. Genitalia of normal male and female, gynandromorphs and intersexes are illustrated in Saether & Galloway (1980 figs. 5–6). The female genitalia are also illustrated in Saether (1977 fig. 81 D–E). The immatures (Figs 3 A–C, 6 A–E) are also typical C. plumosus except that the larva has blood-gills of semireductus type (Lenz 1954 – 62: 161; Shobanov 1989). Although the blood-gills overlap in length between C. entis and C. plumosus the head capsule measurements show that only one is species involved. The head capsule lengths of different instars is shown in Fig. 9. Distribution and ecology. C. entis in North America (as C. f. semireductus) is known from British Columbia and Manitoba, and from Washington, Colorado, North and South Dakota, Minnesota, Wisconsin and Indiana (Saether 1970: 8, 1975: 3130; Saether & McLean 1972: 11; Wiederholm 1976: 27; Kiknadze et al. 2000: 859; Martin 2012). In the Palaearctic region C. entis is known from freshwater in Norway, Finland, Estonia, Chech Republic, Russia and Switzerland (Kiknadze et al. 2000: 859, Saether & Spies 2011). In Lake Winnipeg C. entis is the most common Chironomus species in the benthos of the narrows and the north basin (Figs 1, 7). Although many adult specimens were caught in the light traps from 1971 (Fig. 5) even more were caught on the light traps set on the ship in 1969. There apparently are two generations a year.Published as part of Saether, Ole A., 2012, The Chironomus group (Diptera: Chironomidae) in Lake Winnipeg, Canada, pp. 1-19 in Zootaxa 3275 on pages 9-10, DOI: 10.5281/zenodo.28083

Chironomus (Chironomus) tuxis Curran

Chironomus (Chironomus) tuxis Curran Chironomus tuxis Curran, 1930: 31. Material examined. Lake Winnipeg light traps: East of McCreary Island, 1 male, 31.vii. 1969; 12 km ENE Winnipeg Beach, 2 males, 17.iii. 1970. The adult males examined have an AR of 3.22–3.44, 6–8 sensilla chaetica on p 2 and 7 on p 3. Distribution. The species was previously known from Manitoba, Ontario and Maine, Massachusetts and New Jersey to Michigan and south to Florida (Townes 1945: 123, Oliver et al. 1990: 43, Martin 2012).Published as part of Saether, Ole A., 2012, The Chironomus group (Diptera: Chironomidae) in Lake Winnipeg, Canada, pp. 1-19 in Zootaxa 3275 on page 13, DOI: 10.5281/zenodo.28083

Cryptotendipes pilicuspis Saether 1977

Cryptotendipes pilicuspis Saether, 1977 a: 98 The male imago is described in Saether (1977 a: 98). Type material. Holotype male, CANADA: Manitoba, Lake Winnipeg, McBeth Harbour, 50 0 08’N, 97 0 30 ’W, 30.vii. 1969, S.S.Chang (CNC No. 14021). Distribution. The species is known only from Lake Winnipeg.Published as part of Saether, Ole A., 2010, Cryptotendipes Lenz from Manitoba, Canada, with keys to known immatures of the genus (Diptera: Chironomidae), pp. 1-20 in Zootaxa 2412 on page 3, DOI: 10.5281/zenodo.19431

Chironomus (Chironomus) crassicaudatus Malloch

<i>Chironomus (Chironomus) crassicaudatus</i> Malloch <p> <i>Chironomus crassicaudatus</i> Malloch, 1915: 453.</p> <p> <b>Material examined.</b> Lake Winnipeg light traps: Victoria Beach, 2 males, 9.vi. 1969; Gull Harbour, 9 males, 16.vi. 1969; Victoria Beach, 1 male, 25.vi. 1969; Matheson Island Government Wharf, 22 males, 26.vi. 1969; McBeth Harbour, 1 male, 30.vi. 1969; Pine Dock, 2 males, 31.vi. 1969; Beaver Point, 67 males, 18.vi. –7.vii. 1971; Old Fishing Dock, 18 males, 16.vi. –11.viii. 1971; Calder's Dock, 35 males, 11.vi. –2.ix. 1971; Hecla Island, 47 males, 27.vii. –25.viii. 1971.</p> <p>Normal non-parasitized males from Lake Winnipeg have an AR of 3.90–4.64, 4.21 (21); 31–64, 44 (10) sensilla chaetica in apical 1/3 of ta1 of p2; and 34–54, 43(10) sensilla chaetica in apical 1/3 of ta l of p2. Male intersexes with completely female antenna and female sternite VIII have 157–190, 171(5) sensilla chaetica on p2;170–210, 198 (5) sensilla chaetica on p3, indicating that these are the numbers found in females. The hypopygia of a normal male and that of a male intersex are illustrated in Saether & Galloway (1980 fig. 8C, D).</p> <p> <b>Distribution and ecology.</b> The species was previously known from natural lakes, impoundments, deep pools of large rivers and deeper farm ponds. It is most common in the southeastern and central United States, extending west to the central plains. All known localities are east of the Rocky Mountains (Wülker <i>et al</i>. 1971: 21, Oliver <i>et al.</i> 1990: 42, Martin 2012).</p>Published as part of <i>Saether, Ole A., 2012, The Chironomus group (Diptera: Chironomidae) in Lake Winnipeg, Canada, pp. 1-19 in Zootaxa 3275</i> on page 8, DOI: <a href="http://zenodo.org/record/280836">10.5281/zenodo.280836</a&gt

Orthocladius

Orthocladius subgen. Euorthocladius Orthocladius subgen. Euorthocladius Thienemann, 1935: 201. Lapporthocladius Thienemann in Thienemann & Krüger, 1937: 266. Diagnostic characters As in Soponis (1990: 6) except for the exclusion of O. rousellae.Published as part of Saether, Ole A., 2005, A new subgenus and new species of Orthocladius van der Wulp, with a phylogenetic evaluation of the validity of the subgenera of the genus (Diptera: Chironomidae), pp. 1-56 in Zootaxa 974 on page 42, DOI: 10.5281/zenodo.17131

Chironomus dilutus Shobanov, Kiknadze et Butler

<i>Chironomus dilutus</i> Shobanov, Kiknadze <i>et</i> Butler <p>(Fig. 2 A)</p> <p> <i>Chironomus (Camptochironomus) dilutus</i> Shobanov, Kiknadze <i>et</i> Butler, 1999: 315. <i>Chironomus (Camptochironomus) tentans</i> auct. nec Fabricius, 1805: 38.</p> <p> ? <i>Chironomus (Camptochironomus) tentans</i> var. <i>pallidivittatus</i> Malloch, 1915: 445, not <i>sensu</i> Edwards 1929, see remarks under next species.</p> <p> <b>Material examined.</b> CANADA, Manitoba, Winnipeg, Freshwater Institute Laboratory Culture, 2 females, 15.i. 1973, J.F. Flannagan; Saskatchewan, LeRoy, 2 females, 7.vi. 1967, A.L. Hamilton. Lake Winnipeg light traps: 3 km off Grand Rapids, 3 males, 13.vi. 1969; 10 km off (Sturgeonskin point) Long Point, 1 male, 14.vi. 1969; 3 km off McCreary Island, 1 male, 15.vi. 1969; Victoria Beach, 1 male, 25.vi. 1969; Grand Rapids Government Wharf, 10 males, 28.vi. 1969; 5 km off Selkirk (Horse) Island, 2 males, 29.vi. 1969; McBeth Harbour, 19 males, 30.vi. 1969.</p> <p> Normal non-parasitized males from Lake Winnipeg have a wing length of 4.07–5.16, 4.61 mm (10); an AR of 3.00–3.86, 3.55 (14); 20–38, 29 (10) sensilla chaetica on ta1 of p2; and 20–43, 25 (10) sensilla chaetica on ta1 of p3. The females have 170–220 (3) sensilla chaetica on p2, 160–250 (3) sensilla chaetica on p3. The male hypopygium and antenna are illustrated in Saether & Galloway gynandromorph, the others caused by mermithid infection (Saether & Galloway 1980 fig. 7A, D, as <i>C. tentans</i>) while the female genitalia are illustrated by Saether (1977 fig.</p> <p>82A–C). Eight of 25 males were intersexes, one a probable gynandromorph, the others caused by mermithid infections (Saether & Galloway 1980).</p> <p> <b>Remarks.</b> It is now realized that Townes (1945) was correct in not recognizing <i>Camptochironomus</i> Malloch as a separate subgenus. Martin (2012) use the name camptochironomus-cytocomplex for species previously placed in the subgenus.</p> <p> According to Shobanov <i>et al.</i> (1999) Nearctic records of <i>C. tentans</i> Fabricius belong to <i>C. dilutus</i> Shobanov, Kiknadze & Butler, but see Spies & Saether (2004) and remarks under <i>C. pallidivittatus sensu</i> Edwards. According to Martin (2012) there are an eastern race and a western race to which the Lake Winnipeg population belong. <i>C. pallidivittatus</i> is a senior synonym of <i>C. dilutus</i> if reexamination of the type not can show that there is no possibility for it to belong to another species such as the Nearctic <i>C. tentans</i> presently found only in Alaska. If such a possibility exists <i>C. pallidivittatus</i> could be declared a <i>nomen dubium</i>.</p> <p> Shobanov <i>et al.</i> (1999: 317) gives the number of sensilla chaeticae as near 80. If they mean ta1 of mid and hind leg combined the number is in accordance with the present specimens.</p> <p> Hein & Schmulbach (1971) found hybridization between <i>C. dilutus</i> (as <i>tentans</i>) and <i>C. pallidivittatus sensu</i> Edwards. Hybridization appears also to be present in the Lake Winnipeg material (Fig. 2 C, D). However, mermithid infections are common in Lake Winnipeg and although most specimens are more severely affected (Saether & Galloway 1980) the illustrated hypopygia could also be caused by more slight changes. caused by parasitazion.</p> <p> <b>Distribution and ecology.</b> <i>C. dilutus</i> is known from lakes, ponds, puddles and brackish waters across the northern U.S. and Canada (Townes 1945: 135 as <i>C. tentans</i>, Shobanov <i>et al</i>. 1999: 315, Martin 2012). <i>C. dilutus</i> appears to occupy the same habitats as <i>C. tentans</i> preferring shallow stagnant waters where the bottom is covered by abundant organic detritus. The larvae are euryoxybiontic and thrive where organic pollution is high (Townes 1945: 126, 136).</p>Published as part of <i>Saether, Ole A., 2012, The Chironomus group (Diptera: Chironomidae) in Lake Winnipeg, Canada, pp. 1-19 in Zootaxa 3275</i> on pages 8-9, DOI: <a href="http://zenodo.org/record/280836">10.5281/zenodo.280836</a&gt

Einfeldia pagana Meigen

<i>Einfeldia pagana</i> Meigen <p> <i>Chironomus pagana</i> Meigen, 1838: 7.</p> <p> <i>Einfeldia synchrona</i> Oliver, 1971: 1591.</p> <p> <b>Material examined.</b> Lake Winnipeg light traps: Beaver Point, 1 male, 27.vii. 1971.</p> <p>Only one adult male was found with an AR of 2.49, a wing length of 3.37, 6 sensilla chaetica in apical third of ta1 of p2 and 4 sensilla chaetica in apical fifth of ta1 of p3.</p> <p> <b>Distribution and ecology.</b> The species is known from the Palaearctic and Oriental regions (Saether & Spies 2011). In North America it is known from British Columbia to Québec, New York, Michigan, South Dakota and Mississippi (Oliver <i>et al.</i> 1990: 46). <i>E. synchrona</i> was described by Oliver (1971) from a shallow, semiartificial cattle pond near Ottawa, Ontario.</p>Published as part of <i>Saether, Ole A., 2012, The Chironomus group (Diptera: Chironomidae) in Lake Winnipeg, Canada, pp. 1-19 in Zootaxa 3275</i> on page 16, DOI: <a href="http://zenodo.org/record/280836">10.5281/zenodo.280836</a&gt