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Distribution and Numbers of Three Globally Threatened Waterbird Species Wintering in Morocco: The Common Pochard, Marbled Teal, and White-Headed Duck
Distribution and Numbers of Three Globally Threatened Waterbird Species Wintering in Morocco: The...
Ouassou, Asmaâ;Dakki, Mohamed;El Agbani, Mohammed-Aziz;Qninba, Abdeljebbar;El Hamoumi, R’himou
Hindawi International Journal of Zoology Volume 2021, Article ID 8846203, 17 pages https://doi.org/10.1155/2021/8846203 Research Article Distribution and Numbers of Three Globally Threatened Waterbird Species Wintering in Morocco: The Common Pochard, Marbled Teal, and White-Headed Duck 1 1 1 Asmaaˆ Ouassou , Mohamed Dakki , Mohammed-Aziz El Agbani, 1 2,3 Abdeljebbar Qninba , and R’himou El Hamoumi Study Centre of Bird Migration, Geo-Biodiversity and Natural Patrimony Laboratory, Department of Zoology and Animal Ecology, Scientiﬁc Institute, Mohammed V University in Rabat, Rabat 10106, Morocco Laboratory of Ecology and Environment, Ben M’sik Faculty of Sciences, Hassan II University, Casablanca, Morocco GREPOM/BirdLife Morocco, Sale´, Morocco Correspondence should be addressed to Asmaaˆ Ouassou; email@example.com Received 3 August 2020; Revised 25 December 2020; Accepted 31 December 2020; Published 21 January 2021 Academic Editor: Marco Cucco Copyright © 2021 Asmaaˆ Ouassou et al. &is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Morocco plays a key role in the life of many migratory birds and their survival, thanks to the diversity and richness of its ecosystems. &e International Waterbird Census (IWC) has been regularly implemented in Morocco since 1983. &anks to this program, a large database on wintering waterbirds’ populations has been collected. In this article, we summarize the wintering data of three globally threatened waterbirds: Aythya ferina, Marmaronetta angustirostris, and Oxyura leucocephala. &e pop- ulation of Aythya ferina, which is declining, is largely distributed in the country, in over a hundred wetlands, 26 of which verify the national importance criteria. Marmaronetta angustirostris has a stable trend over the years even though its population can know high annual ﬂuctuations; it winters in more or less 50 wetlands, among which 18 host more than 1% of its regional population and 16 verify the criteria for national importance. On the contrary, Oxyura leucocephala, a globally endangered bird only encountered in a dozen wetlands, shows a moderate increase in its numbers; only two wetlands verify the Ramsar criterion 6, while a total of six can be considered of national importance. Furthermore, given the conservation statuses of these waterbirds and according to the Ramsar criterion 2, all their hosting sites are of international importance. &e results presented in this paper are a crucial step for the adoption and implementation of adequate conservation measures for the species and their key sites. Nevertheless, com- prehensive research and coordinated eﬀorts on the factors (ecological and anthropogenic) inﬂuencing the species, at the national and international levels, are required for a better understanding of their populations’ dynamics. Waterbird Agreement, the country undertakes regular water- 1. Introduction bird censuses that provide an appropriate basis for eﬀective Morocco is a North African country, with highly diversiﬁed decision-making in their conservation. In fact, Morocco has ecosystems and coastlines along both Atlantic Ocean and been regularly participating, since 1983, in the International Mediterranean Sea [1, 2]. It is located at the crossroads of many Waterbird Census (IWC), one of the largest biodiversity bird migration routes between Europe and Tropical Africa, and monitoring programs in the world, thanks to the coordination its wetlands play a crucial role for thousands of birds as of the Study Centre of Bird Migration (in the Scientiﬁc Institute) stopover, wintering, and breeding areas [3, 4]. &e country has and the collaboration of GREPOM/BirdLife Morocco, which ratiﬁed almost all international and regional agreements for the provides the majority of ﬁeld volunteers. conservation of these birds and their habitats. In the context of &is article provides new syntheses on three globally the Ramsar Convention and the African-Eurasian Migratory threatened species of Anseriformes : the White-headed 2 International Journal of Zoology Duck Oxyura leucocephala (Scopoli, 1769), an endangered Nevertheless, given the large number of wetlands to be bird , and two vulnerable species the Marbled Teal censused, some missions can start in late December (es- ´ ´ ´ Marmaronetta angustirostris (Menetries, 1832)  and the pecially in the Saharan region). Moreover, in some rare st Common Pochard Aythya ferina (Linnaeus, 1758) . cases, data from censuses during the 1 week of February &e Common Pochard is a Eurasian duck found in a were accepted; they were conducted in some sites (Atlas wide variety of wetlands (marshes, lagoons, lakes, artiﬁcial lakes) that were not accessible, during January, because of reservoirs, and rivers), with eutrophic to pH neutral waters, heavy snow. &e number of wetlands censused, at least once, but it mostly prefers large open bodies of water with in the context of this program is 272 (IWC wetlands net- abundant emergent vegetation [8–10]. In Morocco, it is a work). However, not all of them are visited every year, winter visitor, passage migrant, and occasional to regular depending on the availability of human, ﬁnancial, and lo- breeder [4, 11, 12]. Evident nesting cases have been observed gistical resources. &e priority is always given to the wet- in ﬁve Northern marshlands: “Plan d’eau de Dwiyate” lands with the highest waterbirds’ numbers and speciﬁc [4, 13], “Merja Bargha” [4, 14], “Marais de Smir” , “Merja richness. de Sidi Bou Ghaba” (with the highest number of breeding During each visit, the observers (Table S4) counted all pairs, nationally: 25 in 2011) , “Merja de Fouwarate” waterbirds on the grounds, in the water, and even those , and in two Atlas lakes (“Aguelmam Afennourir” and ﬂying inside the site, using binoculars and telescopes. “Dayet ‘Awa’” ). &e threats faced by the species and its Counting points and transects are determined for each limited breeding population have rendered it vulnerable in wetland, depending on its conﬁguration and accessibility. Morocco . When some wetlands are close to one another, in a way that &e Marbled Teal is commonly found in shallow allows frequent bird exchange between them, they are brackish wetlands , with rich emergent and submerging considered as complex sites and are covered during the same vegetation [9, 19, 20], avoiding open-water areas [20–22]. visit. Over the years (especially since the 1990s), most However, its distribution largely varies with seasons, espe- wetlands have been censused by the same group of ob- cially depending on its dietary needs . In Morocco, it is a servers, using the same protocol; this makes the obtained resident breeder, winter visitor, and passage migrant [4, 11]. data more homogenous, comparable, and reliable. &e Its breeding population was estimated to 50–250 pairs , observers participating in the IWC program are ornithol- distributed in a dozen wetlands situated in the north and ogists, qualiﬁed and trained for bird identiﬁcation. New south of the country [4, 16, 17, 23–25]. Nevertheless, it is the observers can join the program after going through training most regularly breeds in four wetlands [16, 17, 24]: “Merja de sessions on bird identiﬁcation and counting methods, both Sidi Bou Ghaba,” “Merja de Fouwarate,” “Plan d’eau de theoretical and practical. During their learning phase, they Dwiyate,” and “Embouchure de Wad Massa.” &e species is can join the established observers’ teams during their census considered endangered in Morocco  mainly because of campaigns to strengthen their training. its habitat degradation and modiﬁcation . &e White-headed Duck is the only Palearctic species of the Oxyurini tribe . Breeding birds are usually found in 2.2. Data Analysis. &e wintering waterbirds’ numbers are freshwater and brackish or eutrophic lakes with dense entered in an information system, which generates auto- matically tables per species and sites. emergent vegetation [22, 27], shallow and permanent or semipermanent , while wintering birds can be found in To calculate populations’ trends, we used the TRIM (TRends and Indices for Monitoring Data) freeware  deeper and larger wetlands, alkaline or saline, and with less vegetation . In Morocco, it is a winter visitor, resident (version 3.54). TRIM generates estimations for missing counts and can analyze data for 4000 sites, over 100 years; breeder, and suspected passage migrant . It is used to th breed in Morocco until the 20 century, before becoming this makes it very suitable for our large dataset, especially since not all sites are visited every year (Table 1). &e missing scarce and disappearing, due its habitats’ loss by agricultural development and droughts . Since the 1990s, the species data imputations take into account a site eﬀect and a time eﬀect, assuming the counts in a year depend on those of the reappeared in “Plan d’eau de Dwiyate” [4, 29] and then expanded progressively to several other breeding sites year before (serial correlation). &e counts are assumed to be Poisson distributed and are converted into annual indices to [30, 31]: “Merja de Sidi Bou Ghaba,” “Merja de Fouwarate,” simulate the missing data and calculate trends, based on the “Barrage ‘Arabat’,” “Barrage El Mehraz,” “Merja Bargha,” completed dataset (with the ﬁrst year as base year, to which cumulating about 60 couples. It is still vulnerable in Mo- the index 1 or 0 is attributed). &e overdispersion (when the rocco . variance is larger than expected for a Poisson distribution) and the serial correlation can be estimated by TRIM, 2. Methodology through a generalized estimating equation (GEE) approach. &e recommended overall slope by TRIM is based on the 2.1. Counting Procedure. Our study is based on the dataset of the waterbirds’ winter census, between 1983 and 2019. &e imputed data and given with the results of the additive slope and the multiplicative slope, which reﬂects the magnitude of counting procedure was adopted according to standard bird monitoring techniques , and the protocol was reﬁned annual change, as well as their standard errors. It is con- verted into one of six trend categories: (i) strong increase: an over the years [14, 33–35]. &e censuses are conducted increase signiﬁcantly greater than 5% per year; (ii) moderate annually, usually during January, to avoid recounts. International Journal of Zoology 3 Table 1: Number and percentage of wetlands visited per year. Year Number of surveyed wetlands % of the IWC wetlands network (272) Average 73 27 1983 47 17 1984 82 30 1985 49 18 1986 35 13 1987 69 25 1988 69 25 1989 56 21 1990 71 26 1991 94 35 1992 86 32 1993 94 35 1994 77 28 1995 89 33 1996 46 17 1997 70 26 1998 65 24 1999 65 24 2000 62 23 2001 65 24 2002 56 21 2003 62 23 2004 65 24 2005 59 22 2006 66 24 2007 77 28 2008 85 31 2009 79 29 2010 62 23 2011 100 37 2012 43 16 2013 78 29 2014 115 42 2015 70 26 2016 88 32 2017 76 28 2018 99 36 2019 131 48 increase: a signiﬁcant increase, but not signiﬁcantly more To better understand the species evolution, we used than 5% per year; (iii) stable: no signiﬁcant increase or diﬀerent parameters, mainly as follows: decline, and it is certain that trends are less than 5% per year; (i) &e average number of a species in each site is (iv) uncertain: no signiﬁcant increase or decline, but not calculated for the long term and short term and certain if trends are less than 5% per year; (v) moderate corresponds to the arithmetic mean. decline: signiﬁcant decline, but not signiﬁcantly more than (ii) &e national average corresponds to the sum of the 5% year; (vi) steep decline: decline signiﬁcantly greater than average numbers in each site. 5% year. A signiﬁcance threshold is also provided for the increasing and declining trends: (i) highly signiﬁcant: (iii) &e total annual numbers correspond to the sum of p< 0.01 (i.e., conﬁdence level of 99%); (ii) signiﬁcant: the species numbers in each site for every year. p< 0.05 (i.e., conﬁdence level of 95%). (iv) &e total number per site is the sum of all the For the Common Pochard and the Marbled Teal TRIM species numbers observed per year in said site. analyses, three periods were considered: long term (v) &e occurrence of a species in a site corresponds to (1983–2019), medium term (2000–2019), and short term the number of winters it has been observed in this (2010–2019). For the White-headed Duck, which has been site. regularly observed in Morocco only starting 2005, the trend (vi) &e census number of a site corresponds to the was calculated for the periods of 2005–2019 (long term) and number of years during which it has been visited. 2010–2019 (short term). 4 International Journal of Zoology (vii) &e occurrence percentage of a species in a site However, this number hides very high interannual ﬂuc- corresponds to the ratio of its occurrence to the tuations (Figure 2), knowing that the total annual num- bers vary between 27 (in 1996) and 3.755 ducks (in 2013). site’s census number. Morocco hosts 47% of the regional population “West (viii) &e 1st census of a site corresponds to the ﬁrst year Mediterranean/West Mediterranean and West Africa” during which it has been visited. . &e species was present in 295 counts and absent in (ix) &e standard deviation was calculated for each site, 651 counts (no observed birds during visits), while 904 to determine the deviation of the numbers ob- data are missing (Table S2). Its population trend (Figure 2) served annually from the average. is stable in the long term (additive slope � −0.0050 ± 0.0092; multiplicative slope � 0.9950± 0.0092), whilst it ��������� is uncertain in the medium term (additive slope � -