Can't get birthday field using Phonegap for bada

Question

While developing an application for bada2 using PhoneGap i'v got a following problem: I tried to refer to my phone contacts and see their birthdays. But when I trying to get the values ​​of the field birthday I always get null. Contact picks up exactly because of alert(contacts[i].displayName) runs smoothly, and I see the name . All contact birthday filled. Field birthday is present in the object contact in cordova.js. So what am I doing wrong?

A simple example alert(contacts[i].birthday return null):

var options = new ContactFindOptions();
options.multiple = true; 
options.filter = "";
var fields = ["*"];
var onError = function (contactError) {
    alert('Error!');
}
try {
  var onSuccess = function (contacts) {
    if(contacts.length != 0){
        for(var i=0; i<contacts.length; i++) {
            alert(contacts[i].displayName);  
            alert(contacts[i].birthday);  
        }
    }
  }
} catch(e) {alert("Error Occured: "+e.message);}         

navigator.contacts.find(fields, onSuccess, onError, options);