Grzegorz Grzywaczewski

Improving Aquatic Warbler Population Assessments by Accounting for Imperfect Detection

Monitoring programs designed to assess changes in population size over time need to account for imperfect detection and provide estimates of precision around annual abundance estimates. Especially for species dependent on conservation management, robust monitoring is essential to evaluate the effectiveness of management. Many bird species of temperate grasslands depend on specific conservation management to maintain suitable breeding habitat. One such species is the Aquatic Warbler (Acrocephalus paludicola), which breeds in open fen mires in Central Europe. Aquatic Warbler populations have so far been assessed using a complete survey that aims to enumerate all singing males over a large area. Because this approach provides no estimate of precision and does not account for observation error, detecting moderate population changes is challenging. From 2011 to 2013 we trialled a new line transect sampling monitoring design in the Biebrza valley, Poland, to estimate abundance of singing male Aquatic Warblers. We surveyed Aquatic Warblers repeatedly along 50 randomly placed 1-km transects, and used binomial mixture models to estimate abundances per transect. The repeated line transect sampling required 150 observer days, and thus less effort than the traditional ‘full count’ approach (175 observer days). Aquatic Warbler abundance was highest at intermediate water levels, and detection probability varied between years and was influenced by vegetation height. A power analysis indicated that our line transect sampling design had a power of 68% to detect a 20% population change over 10 years, whereas raw count data had a 9% power to detect the same trend. Thus, by accounting for imperfect detection we increased the power to detect population changes. We recommend to adopt the repeated line transect sampling approach for monitoring Aquatic Warblers in Poland and in other important breeding areas to monitor changes in population size and the effects of habitat management.

Effect of Habitat Burning on the Number of Singing Males of the Aquatic Warbler Acrocephalus paludicola

Abstract. Wildfires can be the most influential phenomena in landscape dynamics and play an important role in determining avian populations. However, the intentional burning of habitats is still a controversial management practice and is legally prohibited in many countries. On the other hand, fires can positively control, or even slow down vegetation succession of reeds and bushes, and, in particular cases, may sustain a habitat for open marsh nesting specialists. One such species is the Aquatic Warbler Acrocephalus paludicola, a globally threatened habitat specialist that breeds in open fens in Central and Eastern Europe. Because bush and reed encroachment threaten many suitable breeding areas, habitat management is necessary to maintain the open wetlands that Aquatic Warblers require for nesting. To assess whether burning was beneficial, we analysed Aquatic Warbler numbers and distribution in the Chełm calcareous marshes in eastern Poland on plots in different successional stages after accidental fires. Our study showed that numbers of warblers, at least of singing males, were lowest in the year of fire, but increased to higher levels in the year after burning and for several years after burning. We recommend that, in calcareous marshes which support up to 0.5% of the total population of this globally threatened species, intentional burning to control succession should be done before the arrival of warblers in spring in order to ensure burning is an effective management tool.

Song Post Selection in the Aquatic Warbler Acrocephalus paludicola

We investigated the microhabitat characteristics of song posts used by males of the aquatic warbler in Biebrza National Park (Poland). On average, song posts were located at a height of 94 cm and 32 cm from the top of the plant. Males preferred singing from living plants in habitat patches with tall vegetation and a low water level. The only factor significantly affecting the place chosen for singing was vegetation height, and males sang from a higher location as vegetation height increased. Where only lower vegetation was available, males used relatively higher places for singing in comparison with the total plant height. These observations support the hypothesis predicting the optimization of song post height.

The silence of the lambs? Plant diversity in abandoned sheep pens

This study aimed at investigating the species composition and richness of the flora of abandoned sheep pens in comparison to their immediate neighbourhood. Field research was conducted in the Wielkopolska province of western Poland on 25 circular plots (20 m 2 ) located in the middle of abandoned pens within sheep farms, paired with 25 reference plots established in nearby grasslands. Physicochemical properties of the topsoil were modified considerably by sheep in the past, so some effects continue to this day. Abandoned sheep pens did not differ signifi cantly in plant species richness from control plots, but Urtica dioica, Galium aparine and Rumex obtusifolius, were significantly associated with sheep pens. Similar values of Shannon index and the low Jaccard index of similarity between plot types indicate that although these habitats are not richer in plant species, they are refuges of some characteristic plant species, which are absent or infrequent in neighbouring habitats. Moreover, the changes in physicochemical properties of the soil (higher average ammonium NH 4 + -N and nitrate NO 3 – -N content) and vegeta

Tawny owl Strix aluco as a potential transmitter of Enterobacteriaceae epidemiologically relevant for forest service workers, nature protection service and ornithologists

Established taxa within the Enterobacteriaceae wereisolated from cloacal swabs of Strix aluco chicks in nest boxes located at five research sites. ChromID ESBL medium (bioMerieux) was used to select a pool of Enterobacteriaceae strains producing extended-spectrum beta-lactamases. Drug sensitivity of the chosen strains was determined from the full pool of Enterobacteriaceae to 6 chemotherapeutics of different mechanisms of action. The study evaluated the sensitivity of ESBL-synthesizing isolates to substances belonging to penicillins, cephalosporins, cephamycins, clavams, carbapenems and monobactams. Analysis of the results indicated a potential role of Strix aluco in the dissemination of epidemiologically-relevant Enterobacteriaceae, and, importantly, pose health risks to forest service workers, nature protection service and ornithologists. The results can also serve as the basis for further environmental studies.

Occurrence of the medicinal leech (Hirudo medicinalis) in birds' nests

Occurrence and breeding of Hirudo medicinalis were recorded in birds’ nests in the fishing ponds and water bodies used extensively by anglers in south-eastern Poland, in 4 of 11 studied bird species (Circus aeruginosus, Fulica atra, Cygnus olor, Chroicocephalus ridibundus). Factors important for the distribution and density of this leech were: nest height, pH of the water and oxygen concentration in the water inside the nests, the body-length of the nesting birds. Our data show that (1) H. medicinalis chooses nests as habitats that are safe in water bodies rich in predators (particularly fish) and provide stable feeding conditions; (2) fishing ponds and other water bodies used extensively by anglers in a landscape modified by human pressure can be an important secondary habitat for the medicinal leech. As the nesting activity of some aquatic birds apparently favors the occurrence of H. medicinalis, active protection of aquatic birds and creating sites appropriate for their breeding may be an indirect way for the conservation of the leech in such areas.