Breeding success due to delayed maize sowing and impact of exceptional aridity
Lapwing population in the province of Upper Austria
A total of 2000-3000 Lapwing pairs breed in Upper Austria, approx. 90% of which in arable land. Before this project, there were no conservation measures for these specific farmland breeders. The few Lapwings occurring in protected areas breed in late-mown meadows, and their numbers have declined by 44% between 2008 and 2016. The Lapwing colonies in arable land showed very heterogeneous short-term population trends between 2012 and 2016, ranging from plus 167% to minus 52%. At the same time there are indications of strong spatial shifts between the breeding areas (Uhl & Wichmann 2017).
Between 2016 and 2019, BirdLife Austria trialled conservation measures for Lapwing colonies in the Nature Park Obst-Hügel-Land on 2 km² of arable land with a total of 22 to 35 Lapwing pairs. The average plot size in the area is approx. 3 hectares. Participating farmers were offered a choice of three measures by the Nature Park: 1) implementing Lapwing islands according to ÖPUL (Austrian agri-environmental programme) that remain uncultivated over a number of breeding seasons, 2) abstaining from cultivating maize fields between 15 March and 10 May during one season, and 3) small-scale marking and preservation of Lapwing nests.
The province of Upper Austria offers farmers compensation payments between 200 and 700€ per hectare and year for these measures. In cooperation with farmers, the pilot project aimed to test workable conservation measures for the large Lapwing populations in arable land, so that they can be applied on a wide scale in the next ÖPUL programme. The reproductive success, surveyed annually, is considered the critical measure for determining the effectiveness of measures.
Methods of surveying populations and determining breeding success
Weekly surveys were conducted from mid-March until early July every year. All relevant Lapwing sightings and all located nest sites were recorded in daily maps. Freshly hatched chicks (or groups of chicks) associated with individual females were recorded, to determine hatching success. Hatching success is calculated as the proportion of these chick groups – which are often only encountered for a brief period of time – relative to the number of incubated clutches documented just prior to hatching. In the case of weekly surveys, it cannot be ruled out that chicks lost soon after hatching remain unrecorded. Therefore, the stated rates of hatching success must be seen as minimum values. In the case of primary clutches with easily observable nests, the results of this survey method for hatching success can be considered reliable. In the case of replacement clutches in higher vegetation, on the other hand, the values must be seen as rough approximations.
The same goes for the number of fledged young. Chicks and adult birds issuing alarm calls were surveyed from the network of tracks and paths criss-crossing the relatively small plots. When adult Lapwings were recorded warning nearby chicks but the number of young could not be clearly determined due to high vegetation, at a calculated age of approx. 4 weeks such observations were recorded as at least one fledged young.
Thus, the term “fledged young” comprises the number of observed chicks approx. 4 weeks of age, as well as one fledged young per warning couple in the above scenario. Young birds already capable of sustained flight are not considered by this survey method due to their increased mobility. As in the figures for hatching success, the number of fledged young from primary clutches can be considered reliable due to their better recordability, while those from replacement clutches are subject to a greater degree of uncertainty.
Involvement of farmers and extent of conservation measures
After consultation of 12 farm businesses, 6 of them participated in the conservation measures. The measure to abstain from cultivating maize fields between 15 March and 10 May was applied on 47 hectares of area covered by contract. At least 50 primary clutches were saved from destruction by farming machinery through this measure. Between 2016 and 2019, ornithologists marked 36 nests which were subsequently preserved by farmers on a small scale in their further management of the plots. Due to a lack of economic competitiveness of the compensation payments (max. 700 €/ha/year) and due to other, primarily bureaucratic hurdles in the application of agri-environmental measures, the implementation of Lapwing islands over a number of seasons did not prove to be a viable measure.
Hatching and breeding success
Breeding success in 2016 was at least 1.0 young per pair. In 2017 and 2018, this value dropped to 0.55 and 0.4, respectively, and rose slightly to 0.6 in 2019. Multiannual breeding success between 2016 and 2019 was at least 0.56 young per pair in these intensively farmed areas of arable land, or between 60 and 69 young out of 109 to 123 breeding pairs. Despite most unfavourable weather conditions in the exceptionally dry springs of 2017 to 2019, with a high loss of chicks due to predation and/or lack of food, a marked increase in reproduction rate could be achieved – not, however, reaching the reference value of approx. 0.8 for viable populations (Horch et al. 2012, Plard et al. 2019). Between 2016 and 2018, the measure to abstain from cultivation between 15 March and 10 May showed the clearest positive effect on Lapwings’ reproduction (see “Efficiency of measures” paragraphs and Uhl 2019).
The numbers of the 2019 season are typical for the course of breeding seasons in the exceptionally dry and warm springs of 2017 to 2019. The hatching rate of the 21 primary clutches was >67%, bolstered by the conservation measures. Due to the low vegetation on the parched fields, however, most of the chicks subsequently disappeared quite quickly in the second half of April. Only between one and four fledged young survived – tellingly, near a meadow that had been flooded by a beaver, into which the family groups had retreated.
For the subsequent replacement clutches, at least 28 in number, the equally favourable hatching rate was 75%. At between 12 and 18 fledged young, reproductive success from these clutches was far greater than from the primary clutches. In contrast to the extremely dry months of April and June, the month of May 2019 was unusually rainy in Upper Austria, with 21 days of precipitation. This must have significantly benefited the higher survival rate of chicks from replacement clutches, as was the case in the high reproduction rate of the rainy spring of 2016.
There remain uncertainties as to the reciprocal effects between the drying of arable plots, possible associated shortages of food, predation rate, and demonstrably high mortality of chicks.
Development of the local population
From 2016 to 2018, the local population exhibited the usual fluctuations between 23-35 pairs (2016) and 28-32 pairs (2018), only to drop to 23-25 pairs in 2019, likely due to low breeding success. As was the case in larger-scale shifts in Lapwing colonies in Upper Austria, opposing trends were also observed locally. While the colony with the most efficient conservation measures and highest breeding success remained largely stable, the colony with lower reproductive rates suffered declines. Furthermore, Lapwings that had lost clutches or chicks in conventionally managed plots were shown to have spontaneously moved into protected arable plots mid-way through the breeding season.
Efficiency of the measure “abstaining from cultivating maize, 15 March to 10 May”
This measure proved to be the one with the most significant positive effect on breeding success between 2016 and 2018. After delayed sowing of maize, this measure was combined with initial management after 11 May that was as slow and cautious as possible, to offer Lapwing chicks maximum protection and allow them sufficient time and space to retreat.
At least 50 primary clutches were saved from destruction by farming machinery on plots under this contract. Since all clutches were lost on conventionally managed maize fields during initial management in April, the decisive effect of this particular conservation measure was the increase of hatching success. Between 2016 and 2018, at least 37 young fledged successfully thanks to this measure (1.1/pair). Due to the complete lack of reproductive success of 12 pairs under this measure in 2019, the total value for 2016-2019 dropped to 0.7/pair – which is nevertheless almost the reference value for vital populations.
An additional positive effect of the measure to abstain from early maize cultivation was that it produced arable plots with low and sparse vegetation in May, while the winter cereals and early maize cultivated on the surrounding plots was already largely too high and dense at this time. Under specific circumstances (cultivation type of neighbouring plots, local food supply, weather, etc.) the family groups continued to use these plots under contract as foraging areas, even at this later stage.
Subsequent controls showed that abstaining from cultivation until 10 May was sufficient for chicks from early primary clutches that were at least 10 days old, because they were already largely able to evade cultivation machinery. Late primary clutches and replacement clutches, however, came into conflict with cultivation work by machine after 10 May. Such nests were marked and avoided on a small scale. There is no reliable data regarding the survival rate of chicks on fields during maize sowing in the first few days after their hatching.
Despite the usual high hatching rate, the extremely dry spring of 2018 saw the first total loss of reproductive success on one of these plots under contract. All chicks of four breeding pairs disappeared from the parched maize fields within the first three weeks of their life. This sudden disappearance of all young chicks of 12 pairs on two plots under contract occurred again in the spring of 2019. Since there was a lack of short crop vegetation on the neighbouring plots in these seasons, and therefore insufficient cover, increased chick mortality is likely due to a combination of higher predation and lack of food.
Efficiency of the measure “small-scale preservation of Lapwing nests”
36 nests were marked and preserved. This measure was usually applied above a minimum of two nests per plot and predominantly for replacement clutches. Application for individual clutches was the exception. Hatching rate was strongly increased through this measure. However, due to stronger migration of family groups out of these conventionally managed plots, the data regarding final reproductive success is imprecise. In any case, this measure proved to be a door-opener in discussions with farmers and contributed significantly to farmers’ acceptance of Lapwing conservation.
The available data indicates that this small-scale marking of nests benefits reproductive success less clearly than the measure to delay cultivation of maize. Possible reasons under discussion are an increased risk of predation of smaller Lapwing colonies or individual pairs, as well as worse habitat conditions for freshly hatched Lapwings on maize plots that were cultivated early and heavily treated with pesticides.
Based on the experience gained in this project, the following questions appear most in need of clarification to ensure successful Lapwing conservation in Austrian arable regions:
- What reciprocal effects exist between warm, arid springs, food availability for chicks in fields, and predation pressure?
- How do different cultivation forms affect predation rate, and which crop cultivations can help reduce it?
- With which agricultural cultivations (e.g. early-mown meadow strips) can the practicable measure “delayed sowing of maize” be combined to increase chicks’ survival rate in arable regions?
Ohne die Unterstützung durch DI Rainer Silber und Julia Kropfberger vom Naturpark Obst-Hügel-Land sowie Dr. Alexander Schuster und DI Josef Forstinger vom Amt der OÖ. Landesregierung wäre dieses Projekt weder entstanden noch durchführbar. Danke an Mag. Benjamin Seaman für seine Übersetzung ins Englische.
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Horch P, D. Ramseier & R. Spaar (2012): Artenförderung Kiebitz im Wauwilermoos LU. Jahresbericht 2012. Schweizerische Vogelwarte Sempach.14 S.
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Uhl H. (2019): Kiebitz-Schutz im Naturpark Obst-Hügel-Land, Brutsaison 2019, Zwischenbericht. Unpublizierter Projektbericht von BirdLife-Österreich. 10 S.
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