Bird Migration - Science topic

Checkout this book chapter:

and this report:

For birds there are AI based classifies that can detect certain species.

For insects I am guessing image and video processing can be the most reliable approach.

Dear Salah Alrabeei

I suggest you go to through these articles first:

1. https://www.mdpi.com/2079-9292/10/9/999/pdf

2. https://www.frontiersin.org/articles/10.3389/fpsyg.2015.01725/full

3. https://www.techrxiv.org/articles/preprint/Deep_Reinforcement_Learning_Versus_Evolution_Strategies_A_Comparative_Survey/14679504/files/30913186.pdf

Kind Regards

Many felines use the earth's magnetic field for their navigation. Therefore, cats can find their way home even at a distance of hundreds of thousands of kidometers.

I think:

1. Calculate directional level of movement

@ Raheema, I think Radar is the main tool to track the flight behavior of migratory birds. It is also now possible to manufacture a small GPS device that is solar charged, so you don't need to change batteries and use it to track flight patterns of birds.

Please have a look at the following RG links.

I am interested but how can I?

The bird came from Thailand. Thanks!

Thank you to both.

There are several research groups using satellites to observe animal movement from space. Please look for Dr. Martin Wikelski: http://www.orn.mpg.de/wikelski/

ICARUS, short for 'International Cooperation for animal Research Using Space', is a global collaboration of animal scientists to establish a satellite based infrastructure for earth observation of small objects such as migratory birds, bats, or sea turtles.

You can also look for more information from https://www.movebank.org/

While these resources might not go back as far as you would like, they may provide valuable data about current trends in migration for your region of interest.

Hi Michelangelo,

I recommend you to read the following paper:

Guérin, S., Picard, D., Choquet, R., & Besnard, A. (2017). Advances in methods for estimating stopover duration for migratory species using capture‐NDASH‐recapture data. Ecological Applications.

Cheers

Hugo

Hi Katherine, 

Thanks for your answer. I'll have a look at the link. The threshold method is what I used up to now but I consider it lacks accuracy at some point. I'll read more for template fit and probabilistic methods. Thanks,

Yannick

Hey Sejer - I was going to write a suggestion exactly as Tigen has already done!  So, please let this be another vote for passive harmonics.  I would strongly suggest you consider using these methods.  They are safe, accurate, and in your context, I think perfect.  Best of luck with your research!  

David

PS - I would also suggest approaching old ski resorts to purchase used units to locate the transponders.  The biggest and most expensive part of this equipment is the actual transceiver that broadcasts the signal to the diode in the field.  The transceiver is the biggest cost, so you can buy a used unit from an avalanche rescue unit that most ski resorts have and need to regularly update their equipment.

I would contact the authors of this paper. It's possible they may have captured some flight videos that were not the focus of their paper, but may be useful to you: 

I would check out their methods of kinematic analysis as well, some of which are quite new (wand calibration for field based locomotion studies): http://jeb.biologists.org/content/217/11/1843

Hi 

I concur with Olivier's answer. If your goal is to have better data on the whereabouts of your focal species, then if already integrate a GPS unit in your tracking tag, you are more likely to get better data by using the weight to maximize battery size and allowing additional GPS fixes than having the overhead of another, inaccurate sensor and a separate battery.

Having said that, I think that the idea of combining tags (GPS+geolocator) can be very useful if your goal is to improve tracking methodology. If eventually your goal is NOT to get the best possible data on your focal species, but to develop methods for better interpretation of GLS tracks, having this dual dataset will be very useful. This combination (where GPS fix can be regarded as the 'true location' for a given time point since its measurement error is negligible in large scales) will allow you to compare different filters and post-processing approaches of the GLS data, and see which one provide best fit to 'real data'. This comparison can help us to get better inference from GLS data in other system, where dual tracking is impossible. Among other advantages it will also allow you proposed ways one might do to compensate for GLS inaccuracy at different contexts, as you initially planned.

We have taken a similar approach when contrasting ACC-identified behaviors with GPS-tracking of vultures, to validate our behavioral classification (e.g., how many of the behaviors identified as 'feeding' actually happen at a feeding station or a foraging habitat? how many of the 'active flight' behaviors are actually when a vultures is moving fast?).

Eobs, mentioned above were very helpful in implementing custom made set-ups, although integrating the GPS sensor with the light sensors sound nontrivial, and presumably time consuming.  Also, i know Yossi Yovel from Tel Aviv university (http://www.yossiyovel.com/) have a custom made miniature GPS tag for bats that can be integrated with external sensors like sunlight sensor.

Best

Orr  

Plenty of migrants (and to a lesser extent mammals) are stored deep frozen here at ISPRA near Bologna. Just tell me what to do if you don't find samples from more convenient locations.

 Hello Andrew, thanks a lot for your reaction. Unfortunately, although a very interesting article, this is more about flight distance to avoid predators, and a comparison between urban birds (less adapted to disturbance) and non-urban birds. 

Anyway, thanks again and succes with your research there (for us) "down under"!

Anny

Thank you for the new answers. I have some plans how to try to catch Spoonbills, but new methods are still wellcome. The area is large, so I think we should use more methods to catch the Spoons, one or two of them must be working...

Pedro: spending 1-1.5 hour in the colony is not disturbing Spoonbills, we also catch the juveniles there while they are unable to fly. Colonies are found in the middle of the reedbed in Hungary, and Spoons breed together with other heron species. Spoonbills breed on the ground in the Netherlands, and Mauritania, the environment of the colonies are open, co-breeders are gulls, and those colonies are possible to approach by moving in a mobile hide. You can use loops there, because you can see what is happening. You can leave the Dutch colonies without disturbance if bird is not caught and you can pull back the loop(s) also without disturbance. Reed makes impossible to use this method in Hungary, and that would be a big disturbance to spend time in the reed, or going back to check a  walk-in trap regularly in the colony. Walk-in trap is a good idea on the feeding ground, I was also thinking about it, and I think that could work on the small pools. There would be also possible to attract birds to put some fish to those pools.

John: I am also thinking about using special net as a trap. There is a guy in Hungary, he is having a trap which looks like a net-tent when it catches the birds, and to activate that trap it is possible to use radio technic. I didn't know whoosh net, seems also a good solution. I was also thinking about using canon net at a regularly used roosting area, but I'm affraid equipment of canon net would looks strange for the birds, and they may avoid to sit next to that - but, of course we should try it. Canon net was used safely in Spain to catch Spoonbills.

Thank you Victoria and Rien for the hints to the "zooniverse" and the "vogel het uit!", but I think "animaltrack" is so far the platform which comes closest to what could be needed for such a mobile application. Thanks also to Giuseppe Masciopinto for the offer to develop such a tool. I will most probably come back to some of you in a later stage of my brain storming process!

Hi.

In the Canary archipelago we have many banana cultivations in lowland areas of the western and central islands. The avifauna of such habitats is poor, but there are some interesting species like Woodcock (Scolopax rusticola), which can breed inside this "extrange" environment. In any case, I don't know any specific paper or unpublished study on the bird fauna of our banana cultivations, but there is some general information on the subject in different books. With regards to migrants, I have seen very few species in this habitat, like some Hirundinidae (e.g. Barn Swallow of House Martin) or Motacillidae (Motacilla alba alba). When there are some artificial ponds or reservoirs linked to these cultivations you can find, naturally, more species, even ducks and shorebirds, and sometimes breeding populations of Rallidae (Common Moorhen and Coot) and of Grey Wagtail. This last species is common in banana cultivations. 

Best regards. 

If you are tracking the bird real-time, or in retrospect using loggers, the movement patterns of the individual changes with the onset of migratory restlessness when it moves away from the breeding range or it's territory, and the onset of migration  when it heads directly to the wintering grounds. The opposite will be true also in the spring upon their return.

The package GAMLSS in R is much more flexible in terms of error distributions than what the standard exponential family can provide. The fitDist function is very useful in this regard as it optimises the best fit distribution for your particular data. You can use one of these best fits in the gamlss model function. I found much improved diagnostics compared to using the mgcv package or glms. Hope this helps.

I would recommend googling for Beidaihe migration information as that is a major flyway for siberian birds. I would guess birds are moving a week or two earlier before they reach there.

When I was in the Platte River Valley in Nebraska a few springs ago, I was floored by the flocks of Snow Geese. The flocks of Sandhill Cranes were impressive as well. Both were in flocks numbering the tens of thousands.

Hi!  You should include this paper:

S. Herrando, F. Llimona, L. Brotons, and J. Quesada. 2010. A new exotic bird in Europe: recent spread and potential range of Red-billed Leiothrix Leiothrix lutea in Catalonia (northeast Iberian Peninsula). Bird Study 57 (2):226-235.

You have probably already read the below Nature article:

Physics of life: The dawn of quantum biology

Nice very useful information many thanks Héctor Cadena

Are you refering to those connectivity graphs, like Gabriel network?

Take a look at Ch. 13 of Legendre & legendre 2012. Numerical Ecology

They hatch in February and it takes them until mid-summer to grow and be able to fly.

Hi, why not take a look at www.eurobirdportal.org? For a number of species you can find model estimates showing the migration phenologies for the years 2010-2013. Those estimates are based on casual observations collated by citizen science websites like www.ornitho.de . If you would be interested in obtaining those data (which will be publicly available in due time anyway), you might want to contact Gabriel Gargallo (see contact details on EuroBirdPortal website).

Cheers

Hi again.

I have found a very interesting and useful paper about the birds of Socotra Island, which contains some information on the distribution and status of Red-billed Tropicbird there. As the paper in question is freely accesible in Internet, I attach the pdf file of it here.

Best regards. 

Dear Neeraj Sharma,

Noise pollution interferes with communication of birds that communicate to indicate danger, feeding sites, etc., and this can cause the reduction of the communication distance to 1500 meters to 50 meters, according to the biologist Dr. Carlos Barros de Araujo.

Such interference can even make the birds change their corner vocalizarem most acutely in higher noise areas.

Noise barriers along highways can contribute to reduction of noise pollution.

I've done some selectivity studies (habitat use and diet). My first suggestion is to avoid simply dividing use by availability as this ratio is unbound and biased to small sample sizes and either extreme.i use Jacobs index (based on Jurgen Jacobs Oikos paper from the 1970s. This and Strauss 1974 highlight why their methods are better than straight ratios. If you have data on lots of individual birds, then you can calculate a Jacobs index value for each habitat used by each  individual and then test these against a mean of 0 using t-tests. If not, the chi squared method (as described byJuan) or compositional analysis can be used.

Cheers

Matt

While I recommend the distance software, you have to transform your presence/absence data using your relative scale of 0 - 9 on the basis of very common (9) to absent (0), something similar to Braun Blanquet method of classification of old. The emerging data will then be subjected to multivariate analysis of ordination and complemented with the distance software to establish the spatial character in the bird distribution in your area of research.

Thanks to all for your kind responses. As it seems a fixed protocol hasn't been developed so far.

Hello Prof. Busse,

We have met a long time ago but I do not think that you remember me. We have the totals below, only rather recent unfortunately, from the island of Lesvos at 39o 01' North 26o 33' E. Wing (max chord), weight, fat score and tarsus measurments. They are not computerised at present but they could be if they are of some interest. We have larger numbers of Phylloscopus trochilus from some other sites in Greece but for time series of less than 10 years.

Filios Akriotis

Athens Bird Ringing Scheme

1994 105

1995 84

1996 190

1997 46

1998 171

1999 5

2000 35

2001 15

2002 155

2003 29

2004 76

If you want basic information, and can get access to it, then The Handbook of the Birds of the World (http://www.lynxeds.com/hbw/about-handbook-birds-world) is likely to be a good starting point.

Thank you Klaus for this invaluable Information! I just tested the Critical Site Network Tool which is very useful. I would be indepted if you could also send me the .shp file regarding Important Staging Areas.

Dionyssia 

Dear Dr. Mohammed,

You can try the following books for start:

Anderson Brown, AF (1979) The incubation book. The World Pheasant Association.

Ashton, C (1999) Domestic goose. Crosswood Press.

Deeming, DC (2002) Avian Incubation. Oxford University Press.

Kear, J and Hulme, M (2005) Ducks, geese and swans. Oxford University Press.

Further, I work for a small scale commercial duck and goose hatchery in Ireland and I can provide you some information. However as it was mentioned above, Dr. Deeming is a well known poultry scientist who can also help.

Good luck,

Attila

Thank you sir, i will try them out. 

Spring in Malta was one of the worst I can recollect. Many species were only evident in their absence. Only a handful of species were recorded in larger numbers than usual. These mainly included cuckoos, stonecurlews and collared pratincoles. Bee- eaters, swifts and hirundines were recorded in some of the lowest numbers ever. Raptors too were  recorded in low numbers except for Marsh Harriers which passed in good numbers early in the season. However low numbers where recorded later on. All other raptors were recorded in lower numbers than usual. Noteworthy is that a few odd records of raptors moving north is going on to date. These have included an osprey, a handful of honey buzzards and a couple of kestrels. 

The answer given above by G. Bothun makes a valid point that many coastal reclamation projects now include habitat restoration schemes to compensate for the potential adverse impacts that reclamation can have on habitats.

However, I shall assume in my answer that follows that there will be negligible habitat restoration. Impacts of reclamation will depend on the size and nature of the reclamation, the size and nature of the estuary/wetland affected and the useage and composition of the migratory birds using that location. Thus, the impacts are likely to be site specific. However, I forecast the following general types of impacts:

Direct impacts include:

(i) Loss of intertidal feeding areas and roosting/resting areas;

(ii) Displacement of bird populations to adjoining wetlands or possibly to nearby agricultural lands with possibility of bird vs farmer conflicts;

(iii) Migratory species, especially those using coastal areas as stopovers during long migrations are especially likely to be sensitive to losses as they may already be stressed/fatigued by their journey and may be less adaptable than resident species. More specialised feeders may also be more greatly affected as they may find it more difficult to find alternative feeding grounds.

Indirect impacts:

(i) Changes to the adjoining physical coastal environment and habitats instigated by the effects of the reclamation e.g. large reclamations in estuaries reduce the tidal prism, slowing tidal currents and potentially leading to enhanced siltation. Outer estuary areas can become increasingly sandy and so alter the nature of remaining intertidal bird feeding grounds;

(ii) The reclaimed area is likely to result in increased disturbance from the human activities associated e.g. port facilities, airports, residential or amenity areas. This could take the form of noise, light or even more frequent intrusion of people into adjoining areas e.g. increase in watersports/recreational boating can be especially disturbing;

(iii) The reclaimed area may result in increased risk of pollution incidents that could affect adjoining areas e.g. oil spills, hazardous chemicals, sewage, eutrophication etc.

(iv) Increased human usage associated with the reclamation could result in greater risk of escapes of alien invasive species that could adversely affect habitats.

In summary, the diverse and potentially far reaching effects of reclamations means that their impacts can be significantly greater then their actual geographical footprint. That is why robust environmental assessments are required to estimate impacts and define requirements for compensatory habitat restoration. 

A final consideration is the cumulative impact of these factors operating at many reclamation sites across the migratory range or path of a species. That is very difficult to account for or compensate for as reclamation schemes are typically assessed and compensated for on a site by site or local region basis.

I've listed a couple of links below, but more specific searches and literature linking migratory birds and coastal habitat changes would appear to be required. 

I wish you success with your research!

Something else to consider is that, if you're using precip mode as a proxy for precipitation being present in the radar scan, this isn't always perfect. Precipitation (often isolated) may still be present in clear air mode, which can affect any calculations of bird density. Likewise, radars can be in precip mode but with no precipitation around. 

There has been much anecdotal suggestion of birds carrying the eggs of fish and amphibians but I am sceptical. It is often evoked as an explanation for isolated populations but evidence appears to be sparse. From a probability view, eggs and larvae of most spp have very high mortality rates and thus the likelihood of a male and a female reaching breeding age is low, though not impossible. Studies in the Pyrenees have suggested that fish only reach isolated ponds up hill through human introduction. Outside of the mountains, seasonal or occassional flooding is a much more common cause of spread, as Fernando Rey describes.

Which differences do you hear in winter that you also hear in eastern European robins?

Without knowing the sex and origin of the birds, there might be another explanation for hearing differences between wintering and breeding birds. In the breeding season, only the males sing (both sexes are present in the same territory, which the male defends). In autumn/winter, both sexes can be found singing (males and females defend separate feeding territories). The songs of males and females differ; females tend to sing with less variation than males. Thus, in winter quite a few singing robins are females and the difference in song is perhaps noticeable in the field. There is a paper by Hoelzel (1986, Ibis) on this subject.

The Breeding Bird Survey website might help contextualize your observations.

You can look at trend estimates for any number of species in a particular state, region, or across the entire survey area.  It seems a little wonky right now (some links are broken which is not typically the case) but it's a great resource for people interested in knowing whether what they are seeing in their backyard is occurring more generally.

You can find some information on WAHID Interface (http://www.oie.int/wahis_2/public/wahid.php/Wahidhome/Home):

Here is what they document on the outbreak in Romania: "On 25 March, the County Sanitary Veterinary and Food Safety Directorate (CSVFSD) of Tulcea was notified by the Danube Delta Biosphere Reserve Administration (ARBDD) about the identification of 64 carcasses of pelicans in an inhabited area, on Ceaplace island, Sinoe lake. This area is located at the border of Tulcea and Constanta Counties, and no other localities with domestic birds are found on a radius more than 10 km. The entire population of pelicans counted initially more than 250 birds, adults and young. Excluding the dead pelicans (found in different stages of putrefaction), no other birds were observed with clinical signs in the area. Also, in the area were observed other birds species, still unspecified."

And about the outbreak in Bulagaria: "Dalmatian pelican (Pelecanus crispus) real-time PCR positive for HPAI subtype H5N1 was found dead on 22 January in Poda protected area. The samples will be tested for confirmation by inoculation of chicken embryos. The pelican was found dead together with a black-headed gull (Chroicocephalus ridibundus) in the framework of the passive surveillance under the national avian influenza surveillance and control program approved by European Commission. The black-headed gull was tested with negative result for avian influenza."

Measures applied: 

- Control of wildlife reservoirs

- Screening

- Zoning

- Vaccination prohibited

- No treatment of affected animals

There is actually not much that you can do when wild birds are affected. You can only try to prevent transmission to other birds, and especially try to protect domestic poultry flocks by increasing biosecurity measures.

You can gain access to many people working on similar questions here: http://www.migratoryconnectivityproject.org/

Here is a new paper that mayget you started?

Utilisation of a coastal grassland by geese after managed re-alignment

By:Bos, D (Bos, Daan)[ 5 ] ; Boersma, S (Boersma, Sieds)[ 1 ] ; Engelmoer, M (Engelmoer, Meinte)[ 2 ] ; Veeneklaas, RM (Veeneklaas, Roos M.)[ 3,5 ] ; Bakker, JP (Bakker, Jan P.)[ 5 ] ; Esselink, P (Esselink, Peter)[ 4,5 ]

JOURNAL OF COASTAL CONSERVATION

Volume: 18

Pages: 471-479

DOI: 10.1007/s11852-014-0333-0

Published: AUG 2014

I have always used Holohil (Canadian), www.holohil.com. Excellent service and reliable devices. I you give them a call they will provide sound advice and find a solution for you.

"Animal Migration" is a new journal exclusively focused on this general topic:

"Movement Ecology" is another open-access option:

Otherwise, "Ecology" and "Journal of Animal Ecology" have published a lot of work on wildlife migration, ranging from movement studies to physiology to disease modeling.

Maybe you can contact Libor Peske - expert on wildlife tracking over the world - which tracking black storks, eagles, ibis and other species. here is a contact to him - lpeske@volny.cz...He is known for the ability to trap rare species in wildlife.

Dear colleague,

we have 2 examples of the same problem her in Israel with 2 different issues and answers: 1- with the Common Crane - Grus grus - in the northern Hula valley. 2- with the White Pelican - Pelicanus onocrotalus.These birds always were passing in the region from Europe to Africa in autumn and vice-versa in spring. For the cranes: at the beginning of the 90', agriculture in the valley has changed: in place of growing cotton they began to grow peanuts during summer. Few of the cranes in autumn found the remaining peanuts on earth after harvest good to eat. This was good for the agriculture too as a sanitary action. But in autumn, after peanut harvesting, farmers sow wheat seeds  and a lot of cranes began to stop definitively to eat peanuts and good wheat. At the same time was created a new natural / touristic reserve around an artificial lake, and to help for this place and for the farmers they began to fed the cranes in the reserve. Now of hundred of thousands of cranes  which migrate tens of thousands stop here and don't continue to Africa, generations after generations. They don't know this natural way. We have now 2 genetically different populations: 1 to Africa and 1to here only. I think it was a bad affair.

Second example - completely different-  the Pelicans: when they were migrating they always had to stop in the Hula valley to feed on fishes in the natural swamp and lake, specially the yearlings. They are very heavy birds and the migration needs a lot of energy. During the 50' the lake and the swamp were dried. At there place, agriculture was developed, including fish pounds.  During tens of years there was a conflict between the fishermen and the pelicans. After the creation of the artificial lake - fishers voluntary bring each year to the lake tons of small fishes that are not market valuable. Now the conflict between fishermen and pelican still exists but is less acute.

In conclusion: if feeding follows the evolution and the ecology of the birds - good. If not - bad 

They resemble some sort of pupae a little like #3. Cant really see the ends in the photo. Were you able to break them?

If the gulls catch preys that are simply disturbed or lost by the goldeneyes, I would call this commensalism rather than kleptoparasitism. If they actively steal the bivalves once they are brought to surface (and I think this is the case), then it's kleptoparasitism.

In addition to the the PLoS ONE paper above, see also

Ruegg, Kristen, Eric C. Anderson, Kristina L. Paxton, Vanessa Apkenas, Sirena Lao, Rodney B. Siegel, David F. DeSante, Frank Moore, and Thomas B. Smith. "Mapping migration in a songbird using high‐resolution genetic markers." Molecular ecology (2014).  http://onlinelibrary.wiley.com/doi/10.1111/mec.12977/abstract

and

Rundel, Colin W., Michael B. Wunder, Allison H. Alvarado, Kristen C. Ruegg, Ryan Harrigan, Andrew Schuh, Jeffrey F. Kelly et al. "Novel statistical methods for integrating genetic and stable isotope data to infer individual‐level migratory connectivity." Molecular ecology 22, no. 16 (2013): 4163-4176.

The biggest difference I have found in studying urban vs non urban environments is a very practical one:  access.  The number of private properties is astronomical, and this presents significant problems in getting access to locations.  I found this a problem in randomising sampling procedures.  Not an impossible problem to solve, but it needs to be considered, and I found it takes a lot of prior planning to resolve.  

ImageJ should work just fine

In some German literature it is mentioned that arctic Peregrines (obligatory migrants) are looking for the same average temperature in the wintering ground as they find in the breeding ground. I am not sure how general and solid this finding is, but it may have some sense if you compare mean temperatures of the sites in question. There are a lot of Peregrine sat tracking projects (Southern Cross, California or look for the fresh book: Peregrine Falcons of the World), so you can look up the areas and see yourself if there is any link.    

Thanks a lot Paulo.

Hi.

In the book: THE BIRDS OF MOROCCO, of M. Thévenot et al. (2003), there is some information of such topic, especially in the appendix 3, "Ringind and recoveries".

What do you mean by migration of bird ? Is it like you want to migrate workloads from private clouds to public cloud ?

We are far away of you... but thinking about islands I can say that in Colombia (South America) the importance of islands for migratory birds has not been established, but has been shown to be sites of emergency stop. They may also be an option for weak migratory birds not compete for best continental habitat sites. During heavy storms and hurricanes the islands are the opportunity of refuge for migratory birds. These opportunities can be exploited by few raptors who remain on the islands as peregrin falcon.

What is the time span that you are looking at? There are records of Blossom Headed Parakeets being exported to ancient Greece, so it is not impossible that some animals were brought here from other parts. Recently, it has been proposed that the cheetah and Asiatic lion were introduced to India during the Mughal era. There is of course the case of the Javanese sparrow, that is now feral in eastern India. The reference to raj-hans in ancient Indian texts probably referred to swans, which are not present now, except as strays. Besides these, there do not seem to be any birds that do not 'belong' here, i.e. that are isolated on the Indian subcontinent with a wider distribution elsewhere....

Thanks, Yoav. In that case there could very well be some spread of flies and other insects and pathogens that way. I'll think about it a bit more.

The most recent issues of The Auk (130: 211-222) and The Journal of Field Ornithology (84: 121-137) have reviews of the advantages and problems associated with light-level geolocators. Neither paper mentions destruction of the devices, but the Auk paper notes the need for greater reporting of problems such as harness failure. I would say your questions is another good one where more data are needed. The best way to answer that question would be to put dummy devices (same shape, weight, etc.) on non-migratory species or captive individuals of the species you want to use. That way, you can observe them for extended periods and see how they react to the device.

Dear Federico,

there are many, e.g.,

Links back to italy;):

Please have also a look to the answers from others and me to:

Best,

Reinhard

I would bet that the "causes" will never be clear. With anthropic effects everywhere, draining land in some places, increased or decreased rainfall in others - how would one even go about testing for causes?

Sorry, not exactly what I meant. I'll try and explain different.

Some years ago when the bird flu was at its peak, Europe made a temporary ban on import of birds for the pet trade, a ban that was later made permanent.

So, I was wondering. 1) Are there studies that have monitored the bird populations after this stop? Are the bird populations rising as would be expected?

2) If millions of birds no longer are taken out of the bird populations annually in Africa and Asia, I would expect a large negative impact on the crops in these countries. Are there any studies on this?

For Greenland White-fronted Geese, which have a double migration, earlier initiation of the first leg is linked to warming temperatures on the wintering grounds http://link.springer.com/article/10.1007%2Fs10750-012-1174-1 but the little information available suggest the timing of the second leg (Iceland - W Greenland) is largely unchanged.

And of course, certain individuals from the British Trust for Ornithology might be able to assist you. Although, I don't know of any specific person, you could attempt to contact them via the following link.