Seasonal body mass changes in Eurasian Golden Plovers Pluvialis apricaria staging in the Netherlands: decline in late autumn mass peak correlates with increase in raptor numbers

Eurasian Golden Plovers Pluvialis apricaria staging in the Netherlands during the non-breeding season show strikingly constant seasonal changes in body mass with a first mass peak in late November and December and a second peak in late April and May. Despite huge sample sizes, variations in this pattern over successive years in the 1990s and among age classes were minuscule. However, in contrast to the body mass levels at other times of the year, there was a marked decline in the winter peak mass of Golden Plovers from the 1970s/early 1980s to 1989–2000. The decrease, by an average of 29 g, was about half the extra mass previously stored in autumn. This additional mass is known to consist of fat and may be interpreted as an energy store − insurance − for sudden cold spells when a negative energy balance forces the birds to move south and stay in front of the frostline. As the rate of the mass increase in September–October showed no change from the 1980s to the 1990s, changes in food availability are unlikely to explain the long-term mass decline. Also, there were no differences in two factors known to influence energy expenditure and feeding rate, air temperature and rainfall. The one striking environmental change relevant to plovers was the steep increase in the occurrence of raptors in the northern Netherlands in the 1980s, notably Peregrine Falcons Falco peregrinus and Goshawks Accipter gentilis. We argue that the halving of the winter mass peak over a decade is consistent with the hypothesis that under increased risk of predation, birds lower their body mass in order to reduce individual vulnerability, a reduction that may be traded off against an increased risk of starvation.

Glastuinbouw: lagere inkomens, vooral voor groentetelers

De glastuinbouw heeft met 2011 een slecht jaar achter de rug. Vooral door lagere opbrengsten dalen rentabiliteit en inkomen in alle drie de onderliggende bedrijfstypen. Bij de glasgroentebedrijven is de daling het grootst

Champignons: forse terugval inkomen in 2009

De veranderende marktverhoudingen en daardoor lagere opbrengsten hebben geleid tot een daling van de rentabiliteit van champignonbedrijven in 200

Champignons: lagere rentabiliteit in 2008 na goed 2007

Productieverlies door diverse groene schimmels, gedurende het jaar afnemende vraag naar industrieel verwerkte champignons, druk op de prijzen en oplopende kosten zorgen samen voor een teruglopende rentabiliteit van champignonbedrijven

Radio-telemetry observations of the first 650 km of the migration of Bar-tailed Godwits Limosa lapponica from the Wadden Sea to the Russian Arctic

In 1999 and 2000, 45 Bar-tailed Godwits Limosa lapponica were supplied with radio-transmitters during spring staging on the island Texel in the western Wadden Sea. With the use of Automatic Radio Tracking Stations (ARTS) on Texel and in south Sweden, and hand-held receivers on Texel, it was possible to follow the later part of the stopover period on Texel for 34 birds (76%) and the passage over south Sweden for 26 birds (58%). Thus, the method of automatic tracking of overflying migrating shorebirds works successfully where the migration corridor is narrow and predictable, as in the case with late spring shorebird migration from the Wadden Sea towards arctic Russia. The timing of departure from Texel and passage over south Sweden of radio-marked birds, with median dates of 30 May and 2 June respectively, were in agreement with published data on the spring migration of Siberian-breeding Bar-tailed Godwits L. l. taymyrensis. The individual variation in migration dates was larger than expected, with birds passing south Sweden between 25 May and 10 June, indicating that the time-window for departure might be broader than previously thought. There was no clear difference between males and females in timing of migration. The time difference between departure from Texel and passage over south Sweden (average 3.3 days) indicates that most Bar-tailed Godwits do not embark on the long flight towards Siberia directly from the western Wadden Sea, but are more likely to stop in the more easterly portion of the Wadden Sea before the final take-off. This pattern is similar to what has been found in other shorebirds and geese (e.g. Red Knots Calidris canutus and Dark-bellied Brent Geese Branta bernicla) migrating along the same route.

Contour feather moult of Ruffs <i>Philomachus pugnax</i> during northward migration, with notes on homology of nuptial plumages in scolopacid waders

Among the sandpiper family Scolopacidae, the Ruff Philomachus pugnax combines a large seasonal change in the appearance of the plumage with a very pronounced sexual plumage dimorphism. Studies on the east and south African wintering grounds of Ruffs indicate that before northward migration at least the males moult (part of their basic (winter) plumage into a kind of alternative plumage. We studied the details of the subsequent moult into a final (supplemental) breeding plumage by quantifying the presence of three feather types - (1) winter (basic), (2) striped (alternate) and (3) breeding (supplemental) - in breast feather samples of 1441 Ruffs captured on staging areas in The Netherlands during northward migration in 1993-97. Ruffs arriving in March show a mix of winter and striped feathers. In April, the 'breeding feather' type appears in both male and female Ruffs, and partially takes the place of winter feathers as well as striped feathers in males, and winter feathers only in females. The presence of three plumages in Ruffs is thus confirmed for males, but also occurs in female Ruffs and in Bar-tailed Godwits Limosa lapponica. We suggest that striped feathers represent the 'original' alternative plumage feather type of the sandpiper family and that the showy feathers of the, in the European literature fortuitously appropriately named, 'supplementary plumage' represent an additional feather generation. Such colourful nuptial plumages could thus be derived characters that have evolved independently in several scolopacid genera, presumably under particularly strong sexual selection pressures.</p

Baseline and Stress-Induced Plasma Corticosterone during Long-Distance Migration in the Bar-Tailed Godwit, Limosa lapponica

The specific roles of corticosterone in promotion of avian migration remain unclear even though this glucocorticosteroid is elevated in many migrating bird species. In general, glucocorticosteroids promote metabolic homeostasis and may elicit effects on feeding and locomotion. Because the migratory stages of refueling and flight are characterized by distinct behaviors and physiology, the determination of corticosterone levels during each stage should help identify potential processes in which corticosterone is involved. We measured baseline levels of corticosterone in bar-tailed godwits (Limosa lapponica) during two distinct stages of migration: (1) immediately after arrival at a false stopover site just short of theWadden Sea and (2) throughout the subsequent 4-wk refueling period on the Wadden Sea. Plasma corticosterone was higher in arriving than in refueling birds. In addition, corticosterone increased with size-corrected body mass during the refueling phase, suggesting that corticosterone rises as birds prepare to reinitiate flight. Therefore, elevated corticosterone appears associated with migratory flight and may participate in processes characterizing this stage. We also performed a capture stress protocol in all birds and found that corticosterone increased in both arriving and refueling godwits. Therefore, the normal course of migration may be typified by corticosterone concentrations that are lower than those associated with stressful and life-threatening episodes.